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Reviews > Stuff Sacks > Dry Bags > Sea to Summit Ultra-Sil Dry Sack > Test Report by Steven M Kidd


INITIAL REPORT - June 27, 2011
FIELD REPORT - September 26, 2011
LONG TERM REPORT - November 19, 2011


NAME: Steven M. Kidd
EMAIL: ftroop94ATgmailDOTcom
AGE: 39
LOCATION: Franklin, Tennessee, USA
HEIGHT: 5' 9" (1.75 m)
WEIGHT: 220 lb (99.80 kg)

Backpacking Background: I've been a backpacker on and off for over 25 years. I backpacked as a Boy Scout, and then again almost every month in my twenties, while packing an average weight of 50+ lbs (23+ kg). In the last several years I have gained a renewed enthusiasm for the back country. I generally go on one or two night outings and now try to average a 30 lb (14 kg) pack.



Image Courtesy Sea to Summit

Manufacturer: Sea to Summit
Year of Manufacture: 2011
Manufacturer's Website:
MSRP: US $19.95
Listed Weight: 1.4 oz (40 g)
Measured Weight: 1.52 oz (43 g)
Listed Size (Diameter x Height): 8.5 x 21 in (22 x 53 cm)
Measured Size (Diameter x Height): 7.5 x 21 in (19 x 53 cm)

The Sea to Summit Ultra-Sil™ Dry Sack is available in seven individual sizes ranging from 1 L (61 cu in) to 35 L (2136 cu in). I will be testing a kiwi green 13 L (793cu in) version in this test series.

Information as listed on the Sea to Summit website:

The Sea to Summit Ultra-Sil™ Dry Sacks are more than 50% lighter than our super popular Dry Sacks. They’re made of Siliconized Cordura®, which is one of the lightest and toughest waterproof nylon fabrics available. Now you don’t have to choose between keeping your gear dry and keeping it light.

•Super compact and ultra lightweight
•Made of Ultra-Sil™ nylon, a polyurethane coated Siliconized Cordura® for ultimate waterproofing and maximum durability
•Non-wicking Hypalon® roll top closure with stiffener at the top for a better seal
•Soft and flexible with a slippery finish for easy packing
•Nearly transparent allowing good visibility of the contents
•All seams are double stitched and tape sealed
•Smaller sizes have flat bottoms, others are round
•Colors: kiwi green, sky blue and orange

Proper Use:


•Any roll-top dry sack must be closed properly to ensure water can’t get in. Begin by folding the Hypalon™ strip down first and be sure to have at least three rolls before closing the buckle.
•Avoid contact with sharp objects or subjecting the sack to high abrasion, as this could compromise the waterproof fabric.
•Ultra-Sil™ Dry Sacks should only be used to store sensitive electronic devices when used in conjunction with another, heavier-duty dry bag – the “double bag” method. For maximum protection of electronics the use of a waterproof hard case with a mechanical seal should be considered.
•This product is not intended for boating or marine use.


The Sea to Summit Ultra-Sil™ Dry Sack is marketed as an ultra lightweight waterproof stuff sack, and I believe they have certainly succeeded in the lightweight portion! This test series will put the waterproofing claim to the test. I own several of the manufacturer's eVent® Compression Dry Sacks, which I believe are excellent products and the first thing I noticed about this sack was how much lighter it is than the older ones. In fact, the sacks are roughly the same size but this test product weighs in at less than a quarter of the weight of the ones I've used for the last several years.
Before even reviewing the product I also noticed a tag showing the product was made with Cordura®, a product I've found in the past to be lightweight, yet durable. This sack is a siliconized version of the product. I also immediately noticed how thin and translucent the bag was. It was only after reviewing some information that I realized it is designed to be "nearly transparent" for good visibility of items stowed inside the bag. The seams are also taped.

The exterior of the sack is smooth to the touch, while the interior has almost a waxy feeling. I poured a little water on the bag and watched it bead up and roll off. I'm excited to try it in the field.

In planning to test this product I had two initial ideas: 1) to use it on day trips in a canoe, and 2) to strap it to the frame of an external frame backpack that I'm also testing with my sleeping bag stowed inside.

However, after reviewing the accompanied instructions it is clearly stated that this product is not designed for the rigors of river or marine environments and that it is intended for use only inside a bag or backpack. The material is certainly quite thin, and if I were trekking in the bush or off trail I don't believe it would be prudent to use it on the exterior of a pack. If I were hiking on prairies or open fields where there was a minimal chance of encountering sharp objects or abrasions I could see it being used in such a manner. The manufacturer also doesn't recommend submerging the sack for extended periods. And although, I don't intend to test in a creek bottom with my down bag, I did place an old pillow in it and dunk it in the tub while successfully keeping the interior contents dry.

Save the aforementioned precautions, the sack also has a few other care instructions that I will mention. Solvents will damage the waterproof coating, and using a clothes dryer may damage the seam-sealing tape. It is suggested that the bag be hand washed frequently with a non-detergent soap.


Like every Sea to Summit product I've used in the past I am so far thoroughly impressed with the Ultra-Sil™ Dry Sack. I'm excited to test it over the next several months, and although my testing strategy will veer slightly from what I initially envisioned, please check back with updates in the ensuing months.

I'm impressed with the lightweight nature of the sack and the fact that it is simple to see the contents stored within it. I like that it's quite simple to expel the air and create a tight closure as seen in the above image. My only concern centers on the material. The lightweight nature makes it thin. I believe it will hold up well to normal use, but fear any accidental encounter with a pointed object could puncture the bag.




29 - 31, July 2011: Coalmont, Tennessee. Public and Private Trails. A 3-day and 2-night backpacking and hammock camping trip covering 9 mi (14 km) with elevations averaging 1800 - 2000 ft (549 - 610 m) and temperatures ranging from 76 - 103 F (24 - 39 C). Conditions were very dry and hot. Rain-fed mountaintop creek beds were completely dry.

1 - 5, September 2011: Land Between the Lakes National Recreation Area, Tennessee/Kentucky. This was a 4-day and 3-night trip covering 16 mi (26 km) with approximate elevations of 350 - 450 ft (107 - 137 m) and temperatures ranging from 70 - 89 F (21 - 32 C). I backpacked and slept in a hammock. Conditions were dry and warm, but breaks in the humidity made backpacking much more pleasant for me than what I've hike in the better part of the summer.

16 - 23, September 2011: Destin, Florida. This was an 8-day and 7-night beach vacation involving no hiking at sea level, no rain with temperatures in the mid 80's F (29 C).


I used the Sea to Summit Ultra-Sil Dry Sack on several multi-day backpacking trips throughout the field testing phase of this report. The product performed up to my expectations on both trips; however, conditions weren't wet or even damp on either outing. The LBL outing was on a trail between Kentucky Lake and Lake Barkley, so on one instance near the end of the trip, with a pair of socks inside, I dunked the sack into the lake for a quick test. Save a few days perspiration build up they remained dry!

I primarily used it to store a down over-quilt and under-quilt for hammock camping. Together the two are little bulkier than a normal mummy style sleeping bag, but they compressed with no issue in the sack. Of course my key priority was to ensure the down remained dry.

Later in the period while doing some last minute packing for a family vacation to the Gulf Coast I decided to grab the bag. On this excursion I didn't use it to compress any items, rather to ensure electronic items like cameras and phones stayed dry while at the beach.

"Lima Bean"

I own several other Sea to Summit bags and they too impress me, but I am especially delighted with lightweight nature of the Ultra-Sil Dry Sack. It compresses well enough, but does tend to get that 'lima bean' shape when in use. This by no means affects the performance of the sack, but it does bring out the obsessive nature of this neat freak.

Although I'd originally wanted to strap the sack to the outside of an external frame pack, I followed manufacturer instructions and only stowed in on the interior during my backcountry outings. The material is quite thin and feels delicate, yet it did hold up well during the week it was used at the beach. There were no punctures, tears or abrasions. Granted the sack wasn't placed under too severe a stress a two and four year old repeatedly tossing it out of a beach bag to get to their sand pails. Though the previous statement may appear a little comical, it is most certainly true that the sack was put under a more strenuous test during the beach week than any time which I utilized it in the field. Because I perceived the material as delicate I probably handled it with more care than necessary each time I used it.


Overall I'm quite impressed with the Sea to Summit Ultra-Sil Dry Sack. In my opinion it is an ultra-lightweight stuff sack that does what it is intended to do...keep items dry inside a pack. It can handle a bulky load of several down quilts and compress to an adequate storage size. I have nothing but positive comments to state about the product at this time.



Ultra-Sil and another Sea to Summit E-Vent sack

7 - 8, October 2011: Arrington, Tennessee. This was an overnight outing to a local farm with a fishing pond that I took with my children. We fished and hiked the fields and wooded areas around the water. Elevations were approximately 750 ft (229 m) and temperatures ranged from 52 - 84 F (11 - 29 C). I packed our gear in and out which was a little under a mile (1.6 km) in each direction and my pedometer showed that we hiked an additional 3 mi (4.8 km) during the outing. The three of us managed to sleep snugly in a two-man tent.

18 - 19 November 2011: South Cumberland Recreation Area on the Fiery Gizzard trail, near Tracy City, Tennessee. This was a dry but cool overnight outing with temperatures ranging from 51 F (11 C) and as low as 30 F (-1 C). Elevations ranged from just under 1500 ft (457 m) upon descending to Foster Falls and rising to around 1720 ft (524 m) climbing out of the gulf onto the Cumberland Plateau.


I've continued to enjoy using the Sea To Summit Ultra-Sil Dry Sack throughout the final phase of the test period. Weather on my outings was atypically dry, but I was certainly able to put the bag through several scenarios to verify how well it keeps the interior items dry.

As mentioned earlier in the report I use a hammock sleep system that incorporates both a down overquilt and an underquilt. Wet down loses all insulating capability, so rather than using two individual non-waterproof stuff sacks I've began using the dry sack to transport both items in the backcountry. I've decided it will continue to be a key storage component for these items. In the rare occasion moisture may make its way into my pack these key items will stay dry.
In the Creek
Once in camp I've also began placing items to which I prefer quick access into the sack and hanging it from the ridgeline of my hammock. Overnight moisture from dew and frost has never entered the bag, thus the interior contents have always stayed dry.

I also previously mentioned that I gave the bag a true submersion test in an earlier phase of the test; however, I lost digital images from that summer trip. On a recent fall trip to the mountains I figured I'd grab a shot for those reading this report. Fortunately for the reader I was able to snag the photograph; unfortunately for me the autumn mountain creek water was not nearly as warm as the lake water from my submersion test in the summer! The key takeaway is that neither interior contents nor the inside of the bag had any moisture. The silicon also sheds water in a beading manner and the exterior dries rather quickly after being introduced to wet environments.


Hangin' In the Backcountry

There isn't much to add concerning this product. In my opinion Sea To Summit makes innovative and high quality items and this is another win. The material is lightweight and saves ounces, yet it protects any interior contents from moisture. There could be durability concerns if used outside a backpack, but the manufacturer clearly states that the sack is intended for use inside a backpack.

I plan to continue using the Ultra-Sil Dry Sack on nearly all backpacking outings in the future.

I'd like to thank BackpackGearTest and Sea to Summit for allowing me the opportunity to test this quality product.

This report was created with the Report Writer Version 1.5 Copyright 2011. All rights reserved.

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