Guest - Not logged in 

Reviews > Clothing > Base Layers and Undies > DeFeet UndShurt > Test Report by Will Dalen Rice

July 01, 2008



NAME: William Rice
AGE: 27
LOCATION: Charlotte, North Carolina, USA
HEIGHT: 5' 7" (1.70 m)
WEIGHT: 145 lb (65.80 kg)

I began backpacking at the age of 13 when I first went to summer camp (1993). In 1999, I started working with a college tripping organization in outdoor trip logistics (in gear preparation), and then as a leader. My most frequented hiking locations are in the Carolina Appalachians and the Smoky Mountains during the cold early spring and the summer. I stopped being a trip leader in 2004, and now I average about 4 backpacking trips and 4 day hikes per year. I carry between 25 and 35 lbs (11.3-15.8 kg) on multi-day trips.



Manufacturer: DeFeet
Year of Manufacture: 2008
Manufacturer's Website:
MSRP: US$ 30.00
Listed Weight: None
Measured Weight: 0.15 lbs (100 g)
Size: Medium
Other details: Sleeveless Model, white

Just out of the package


The shirt came in what appeared to be a Ziploc type bag. I was unable to figure out how to get it open though, so I cut the top. Then, the next day I figured out how to reseal it, after having "broken" it. The bag is fully recyclable, but a note suggests reusing the bag to pack gear with. Interestingly enough, the english note says to use it in innovative ways, such as to "pac" your gear for cycling and running events. The french note says "DON'T THROW AWAY!" and then goes on to say you can use it to keep your telephone safe while you run or bike.

There are no directions with it. I had no trouble figuring out how to use the shirt. It does have wash instructions, a size chart, and a synopsis of how it works and its features. These are all included in English and French.

When I first put it on, I couldn't help but smile. The shirt is incredibly soft and smooth feeling. It is also so light it barely feels like I am wearing anything. It is like wearing soft air.

The shirt is made of 64% Polyester, 19% Hydrofil Nylon, and 17% Spandex.

Initial Concerns:
The shirt is white. I own plenty of clothes that started out white, but none that are currently still white. How well will it wash?


The day after I got it we went orienteering. We spent about 4 hours hiking around in the woods on easy terrain. There was occasional running, but it was mostly brisk walking and most of it was off-trail. I wore a polyester, long-sleeve shirt as my outer layer. It was very thin and tight fitting. I was surprised that I stayed warm the entire time, despite having only two layers, both of which were thin and neither of which are windproof.
Conditions: Cloudy w/ traces of Rain, Avg. Temp.- 46 F (7 C), Humidity- 70%, Wind- Calm

The second day, I took the shirt running with me. It was much warmer, but I wore a mostly cotton t-shirt as a 2nd layer anyway. I was comfortable with the short sleeve shirts on standing in the sun, so was interested in how I would do with heat while running. I ran 1.5 miles. The last half mile I was beginning to sweat around my hairline. I could feel the undershirt was damp. I took my outer shirt off and it was showing a little perspiration around the collar and the armpits. Within 10 minutes (while walking to cool down), my undershirt was back to dry again.
Conditions: Sunny, Avg. Temp.- 64 F (18 C)


This shirt will become standard wear for running (trail and greenway), Orienteering, Bouldering/ Climbing, and any other hiking I end up doing.

Planned Events:
Hiking in Mexico- early March
Orienteering in Chatahoochee Recreation Area, Georgia- mid March
Hiking at Stone Mountain, Georgia- late March
Hiking at Mt. Mitchell, North Carolina- early to mid April
Climbing somewhere in North Carolina- April


-Light and Comfortable
-Keeps me cool and dry when sweating

-Too clean to stay that way



Location: Teotihuacan Aztec Ruins, Outside Mexico City, Mexico

Bottom of Pyramid

Top of Pyrmiad

Weather: It was super sunny, 80 F (26.7 C), and dry (30-40% humidity)
Elevation: 7500 ft
Terrain: There were lots of stairs and lots of elevation gain (216 ft to the top of the sun pyramid)
Other Clothes: Long sleeve, white cotton t-shirt worn intermittently to keep sun off shoulders
Activity: We went on a walking tour that lasted about 1.5 hours. Then we spent another 1-1.5 hours walking up the highest pyramid and generally wandering around amongst vendors peddling their wares. Another hour was spent shopping in an outdoor courtyard.

I expected that in the dry heat of Mexico, I would sweat to keep cool but wouldn't stay wet. The UnDShirt pulled the moisture away from my skin rapidly. I was not wet to the touch anywhere while wearing the shirt alone and walking on the flatter terrain. When I put on the long sleeve cotton t-shirt, I sweat more on my lower back, and the shirt was moist to the touch. It took about 20 minutes of climbing stairs to get to the top of the tallest of the pyramids and left me sweating on my head, under my arms, and around my collar. Within 5 minutes of reaching the top though, the wind (approx. 10-20 mph/ 16.1-32.2 kph) had dried the shirt and cooled me off enough that I needed to put the long sleeve shirt back on.

Unexpected Benefit:
Both myself and the shirt tended not to become really smelly, even though I was sweating. In general, it seems as though the shirt doesn't hold any negative smells, despite doing athletic and dirty activities while wearing it.

Location: Running, Chattahoochee River Park (Atlanta, Georgia, USA)
Weather: Moderate Temperatures (see Summary, Spread of Use), Sun, Cloudy, Minor Rain
Elevation: not significant, no change
Terrain: flat, black top
Other Clothes: shorts
Activity: Running 2-3.1 miles (3.2-5 km) at a time

Since I run often, this has been the best opportunity for me to compare the UnDShirt with other clothes I use for my active lifestyle. The UnDShirt is 90% acrylic and 10% polyester. Otherwise, I run in sleeveless cotton t-shirts (100% cotton), a surf shirt (85% polyester, 15% cotton), or a short sleeve t-shirt (10% polyester, 90% cotton). Of the clothes I own, the UnDShirt keeps me the coolest, smells the least after use, and dries the fastest. It also holds the advantage of sun protection over not wearing a shirt at all.

Location: Stone Mountain, Georgia, USA
Weather: Sunny, 80.5 F (26.9 C), Breezy at the top (10-20 mph/ 16.1-32.2 kph)
Terrain: Rocky, final elevation of 1683 ft (510 m)
Other Clothes: Convertible pants/ shorts
Activity: I went to try out a new ultralight backpack and the amount of gear I would be carrying (35 lbs/ 15.9 kg) on some longer trips this summer. It was intended to be a worst case scenario test of my cardio condition and ability to carry a heavy backpack. There was a lot of bottled water as weight involved. I was with a dog and my girlfriend (dogs aren't allowed on the mountain). So, I made a speedy hike to the top and back alone. Total distance traveled was 2.6 miles (4.2 km). I spent roughly 45 minutes hiking up, 20 minutes at the top, and about 20 minutes hiking back down. There was another roughly 1-1.5 hours spent with my pack on hiking around the mountain and another 1-1.5 hours just walking without the pack.

The thin material of the UnDShirt did not do much against the rubbing of my backpack straps. It was a little bit uncomfortable. Sweaty areas developed around my shoulder straps and back pads (upper and lower back). Once I reached the top, the wind quickly dried my shirt. The shirt's breathability really helped to cool me off.

Location: Vickery Creek Orienteering (Chattahoochee National Forest, Roswell, Georgia, USA)
Weather: Cold- 42-47 F (5.6-8 C), humidity of 74-92 % with traces of rain
Elevation: 300 ft (91.4 m) of gain
Terrain: lots of up and down due to poor planning of route
Other Clothes: Dri-Clime Jacket and spandex shirt to begin with, shed jacket layer 20 minutes in, shed shirt layer 10 minutes later
Activity: Orienteering through bramble and briar areas, pretty much ran, jumped over stuff, down into stuff, up out of stuff, fell, crawled, and got back up for 90 minutes. There was 300 ft (90 m) of elevation change from the start to the ridgeline, and due to poor planning and inexperience, I ran up to the ridge and back down multiple times. I was straightlining my route from marker to marker, which often meant crossing a lot of contour lines while crashing through dense thickets.

Initially, I was cold. It was a little breezy and my footwear and headwear weren't doing much to keep out wind. Also, I had no gloves, so the hands were cold. Once I began, I heated up very fast. Then, after shedding both my two outer layers, I was comfortable in just the UnDShirt.

I expected to see a large amount of pulled threads from the shirt when I was done. I had at least 2 bleeding scratches on my lower body and 2 bleeding scratches on my torso when I got in the shower. Below is the picture of the shirt with arrows to show where the thread runs are. The shirt held up very well. I also expected that after this, the shirt would fall apart rather quickly. It has not done this and looks the same now as it did when I was done orienteering, despite much more use.

Post Briar 1

Post Briar 2

Location: Panola Mountain State Park, Georgia, USA
Weather: Sunny, Windy (5-10 mph, 8-16 kph)
Elevation: no significant change, less than 1000 ft (300 m)
Terrain: slight uneven terrain
Other Clothes: Nomex long sleeve shirt, Nomex pants, Hard hat, gloves
Activity: Setting a prescribed fire, noon to 6 pm. I volunteered with the Georgia Department of Natural Resources office to help set and control a prescribed forest fire. Most of the burning was of a light, fluffy broom sedge grass. This made for brief, large flames of 5-10 ft (1.5-3.0 m) that traveled quickly. There was no sustained heat after the fire passed, but near it while being lit was hot enough to require a hand to shield my face.

I was sweating a lot, due to the physical exertion and due to heat from the sun and fire. I did not notice any pooling of water next to my skin and the shirt never felt wet enough that I could notice it on my skin. My Nomex also did not seem to become wet to the touch. When I took off my Nomex jacket, the shirt was moist, but the light winds quickly dried me off.

Location: Charlotte Fire Fighting Academy (Charlotte, North Carolina, USA)
Weather: Sunny, 82 F (27 C), hotter on black top, 9 mph (15 kph) winds, 58 % humidity
Elevation: not significant, no change
Terrain: NA
Other Clothes: hard hat, gloves, BDU pants (thick cotton/poly blend), 50 lb (22.7 kg) weight vest
Activity: Candidate Physical Aptitude Test (practice run). The test is a timed event consisting of the following activities: Stair Climb at 60/ minute for 3 minutes (with 75 lbs of weight added, all other events with 50 lbs of weight added), Ladder Raise, 20 and 30 lbs (9 and 13.6 kg) equipment carry, hose drag, sledge hammer breaching simulator, dark search maze, 165 lb dummy drag, and the ceiling breach simulator.

The shirt did really well. I was required to wear a 50 lb weight vest the entire time over the shirt. While still on the stair climber (the first event), I could feel my legs beginning to sweat. When I was done with the entire test, my torso was wet with sweat, but it dried quickly when I took off the vest.

Location: Travel Day- Charlotte, North Carolina, USA to Mexico City, Mexico
Weather: inside with temperature fluctuations from 65-80 F (18.3-26.7 C), outside temp change from 40 F (4.4 C) in Charlotte to 90 F (32.2 C) in Mexico City.
Terrain: NA
Other Clothes: Worn with loose, long sleeve shirt (medium thickness), polyester. Also wore zip-off, North Face pants.
Activity: Transport to airport, waiting in airports, boarding airplanes, sitting in them, flying in them
Although this shirt is intended for outdoor use, I think it also is intended as the first line in a layering approach to dressing. I have always had a problem with dressing for airplane travel, since there is a frequent change in temperature that is often drastic (i.e. hot airplanes sitting on the runway pre-flight and much colder airplanes in-flight). This shirt was worn under these rapidly changing conditions to test how comfortable it stayed when I was unable to change my clothes or do anything else to adjust my condition (i.e. when the fasten seatbelt sign was on).

When I wore this shirt as a base layer, it was light enough and soft enough that I really still felt like I was just wearing one shirt. Because it is close fitting, it combined well with a warmer outer layer that fit loosely, keeping me warmer. When the heat was present and I began to get uncomfortable (ex: sitting in a hot plane waiting to take off or just about to walk out of the baggage claim into the Mexican heat), the shirt cooled and pulled moisture away from skin. A couple times, I could feel my calves sweating in my nylon pants, but my torso was nice and cool.


Fully saturated shirt weighs ~1 lb (~500 g)
Wrung out shirt weighs ~ lb (~250 g)

Is it comfortable? Does it fit well and stay in place during lots of motion? Does it restrict motion?
The UnDShirt fits me snuggly, but because of its light weight construction, it doesn't feel like I am being squeezed by it. It also does not bunch up or get moved around much while I am wearing it under other layers. The sleeveless model gives unrestricted arm motion, and again, because it is so light, twisting in my torso or bending/moving does not feel restricted by this tight fitting shirt.

Does it keep me drier when I am sweating?
If I am wearing a layer on top of the shirt, sweat can get trapped. However, when standing in any kind of wind condition (anything more than calm), the shirt evaporates sweat very well when it is all I am wearing.

Does it keep me warmer when it's cold?
When worn with another layer, the UnDShirt does help keep me warm. By itself, it is not a significant shirt for retaining body heat.

Does it chafe? No. It rides very smoothly and doesn't move around much.

How durable is it when used more than once a week?
The shirt is still in very good condition, and I have been using it a lot to run in and do other things in the outdoors. I don't wash it very often and sometimes I will only rinse it, but it doesn't hold any bad smell from my sweat.

Does it stain, or come clean when I wash it? It is still white, which is uncommon among my clothes.

The shirt did not get a chance to go snowboarding with me, due to the short nature of our snow season and my inability to plan and execute a trip to West Virginia (USA).

I also never made it to Mt. Mitchell and didn't get a chance to go climbing with it yet.


I used the shirt by itself, as a base layer with a light shirt over top, with a long sleeved heavier shirt over top, and with a long sleeve shirt and light jacket. I used the shirt 2-3 times per week for the 2 month Field Reporting Period. When running, I used the shirt for up to 30 minutes. On the weekends I used the shirt for a day at a time, wearing the shirt for 2-4 hours of activity, and another few hours before and after.

Spread of Conditions:
I used the shirt between 42-90 F (5.6-32.2 C), wind speeds varying from calm to 10 mph (16 kph), and humidity ranging from 30% all the way up to the high 90s. The shirt was worn in clear sky/ sunny days, cloudy weather, and weather with traces of rain.


- Shirt does not get smelly after sweating in it (can be rinsed in sink instead of machine washed)
- Washed shirt comes clean, shirt is still white
- The shirt breathes really well
- Shirt stays in place really well
- Extremely light weight and doesn't bunch
- Works really well as a base layer for layered dressing
- The shirt is durable, has not fallen apart despite interaction with thorns

- Not thick enough in shoulders for carrying heavy backpack


The shirt will come with me:

- on the Appalachian Trail for 17-20 days in mid-June
- bouldering/ climbing in Charlotte
- to the final test day for the Charlotte Firefighting CPAT

I will continue to use the shirt while running.

I also hope to do some more orienteering with this shirt.




Date: April-July
Location: Chattahoochee River
Weather: Sunny, 70-85 F (21-29 C)
Elevation: 1000 ft (300 m)
Terrain: Flat
Other Clothes: shorts
Activity: walking the dog, 1-2 miles, 2-3 times per week

I placed my UnDShirt right next to the door, so after the morning shift at work, I would come home, change into it, and head down to the river to walk the dog. This was a frequent occurrence, so I got to wear the shirt a lot in moderate conditions. It was always comfortable, helped reflect a lot of the heat from noonday sunshine, and breathed very well, even with just moderate movement.

Date: 5/20
Location: Sope Creek, Chattahoochee River National Recreation Area, Atlanta, GA, USA
Weather: sunny and warm (84 F/ 29 C)
Elevation: 1000 ft (300 m)
Terrain: hills
Other Clothes: shorts
Activity: hiking, playing in creek, and relaxing (5 hours)

This was another typical day of hiking and exploring nearby forested areas. While rock hopping in the creek, I did manage to slip on some muddy rocks and take a tumble. I ended up smearing the shirt with some muck. I was worried that it would not wash out, since the shirt is white and river muck is sometimes stubborn. The shirt did wash clean when I got home. During the hike in and out, I did not noticeably sweat. It was not difficult hiking.

Date: 5/23
Location: Atlanta, GA, USA
Weather: rain, 75 F (23 C)
Elevation: approx. 1000 ft (300 m)
Terrain: less than 10 ft (3 m) change
Other Clothes: shorts
Activity: running, 1-2 miles

Performance: The shirt did not keep me dry in rain and actually soaked up water pretty well. However, the shirt did not gain a large amount of water when it was fully soaked, so running in the fully soaked shirt was not that big of a difference. Once I stopped running, the shirt did not feel clammy on my skin, like a wet cotton t-shirt does.

Unexpected Benefit:
The DeFeet UnDShirt is still easy to take off, even when it is very wet. It did not stick to my skin.

Date: 5/27
Location: Island Ford Park, Chattahoochee River National Recreation Area, Atlanta, GA, USA
Weather: sunny and warm (82 F/ 28 C)
Elevation: 1000 ft (300 m)
Terrain: hills
Other Clothes: bathing suit
Activity: hiking, playing in river

The shirt works as a very versatile piece of equipment for day outings in Georgia in the summer. This particular day, we went down to the river to cool off. It was sunny and warm, so the shirt had a chance to reflect some of the sunlight away and otherwise pull sweat off me to keep me cool. The water temp was a cool 50 F (10 C). We threw the Chihuahua in the water and he didn't like it very much. The shirt stopped his shivering when we wrapped him in it to get dry. I went for a swim also, and then used the shirt as a pillow while laying on a hot rock. Then, when we were all done, I put the shirt back on and we hiked the 1 mile (1.6 km) back to the car. The shirt was by then completely dry.

Date: June 5th- 10th
Location: The Appalachian Trail Mountains of North Georgia, USA
Weather: 65-85 F (17-29 C), humid (40-50%), sunny, wind of 0-5 mph (8 kph)
Elevation: 1000-4000 ft (300-1300 m)
Terrain: very rugged, gained/ lost minimum of 2.2 miles (3.52 km) over 40 miles (64 km) walking distance
Other Clothes: convertible pants/ shorts
Activity: hiking with 30+ lbs (13.6 kg) pack, more than 10 miles (16 km) per day

I was particularly excited about putting this shirt to the large test of being one of the few pieces of clothing to take on the Appalachian Trail (AT) with me. I started out on the first day wearing the DeFeet Shirt and a pair of zip-off pants. The shirt was still very effective at wicking sweat away from my body where the backpack was not covering it. The shirt held moisture on my back and where the hip belt and shoulder pads touched, because the moisture could not evaporate. Since the shirt is very light and sleeveless, my backpack straps did not work well with it. I either felt the straps through the shirt, or worse, they actually pressed down on the shirt seams and pattern to irritate my shoulder area. After the first day, I decided not to wear the shirt with my backpack on. So, it became my camp shirt for wearing at night.

Shirt off center

There were two possible ways which this shirt seemed to fail me while backpacking. In this picture, the shirt has moved at my left shoulder. It did this because of movement in the backpack or maybe just movement of the shirt from hiking. Either way, the strap is now on top of the "sleeve" seam, which caused irritation.

Shirt centered

If the shirt was in place like it was supposed to be, it looked like this. This situation caused problems as a result of the neck seam's interaction with the straps.

As I mentioned earlier also, even disregarding the seams, the way my straps felt through the shirt was not particularly comfortable due to the noticeably woven fibers of the shirt.

The UnDShirt still dries really quickly. I washed it multiple times while on the AT. After wringing it dry and hanging it on my backpack, it was ready to wear in a couple hours. It started to retain odor more since I was wearing it and sweating in it and I was getting dirtier. Rinsing it in water though was adequate to get rid of the smell.

The shirt has begun to retain a little bit of dirt and is beginning to show some wear and tear. It is no longer as white as it once was and it is generally becoming fuzzier.

Slightly Fuzzier

Unexpected Benefit:
At one point in time, I managed to bash my hand with a rock by accident. I began to bleed, and so I used my shirt to hold my finger, to help the wound stop bleeding. The blood that got on my shirt didn't rinse off in the creek, but it did come clean in the washing machine once I got home. I was glad it did not hold the blood stain, but the shirt is still definitely less white than it used to be. I have not attempted to bleach it.

Since the shirt has a sort of textured weave, it works really well for bathing/ scrubbing. It holds just the right amount of water that I want when wiping myself clean after hiking all day in the steamy Appalachian Mountains.


The DeFeet UnDShirt has become a pretty common part of my life. I really enjoyed its tight fit, which still did not compromise its breathability. It is also so light, that I felt it has most of the benefits of no shirt while still wearing one. It did extremely well in light-use situations for me and was perfect on short trips. On longer backpacking trips, it lost a little bit of value since it did not work well for me with my back pack straps. It still was worth carrying to me though, and even though I sent stuff home, I never thought of jettisoning the UnDShirt.

- light
- white color keeps cool in direct sunlight
- sleeveless design gives sides more ventilation

- white color shows dirt real well and has become less white through use
- seams and texture of shirt make it not comfortable when backpacking


This shirt will continue to be used on day trips to everywhere, especially places with water activities. I will also wear it with layers to cold weather activities that eventually have me overheating (ex: speed orienteering).

I have not made it out to climb in yet, but plan to soon.

I won't bring it as a primary shirt for backpacking, but will likely use it as a secondary, in-camp shirt. It is too light and versatile, even when really trying to cut back on weight, to leave at home.

I think it is going to work well as a snowboard base layer shirt also, so I am excited to try that this winter.

This report was created with the Report Writer Version 1. Copyright 2008. All rights reserved.
Read more gear reviews by Will Dalen Rice

Reviews > Clothing > Base Layers and Undies > DeFeet UndShurt > Test Report by Will Dalen Rice

Product tested and reviewed in each Formal Test Report has been provided free of charge by the manufacturer to Upon completion of the Test Series the writer is permitted to keep the product. Owner Reviews are based on product owned by the reviewer personally unless otherwise noted.

All material on this site is the exclusive property of
BackpackGearTest software copyright David Anderson