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Sea to Summit Ultra-Sil Day Pack Review

A bare-bones ultralight pack for those really dedicated to cutting out ounces
Sea to Summit Ultra-Sil Day Pack
Credit: Sea to Summit
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Price:  $40 List | $39.95 at REI
Compare prices at 2 resellers
Pros:  Insanely light, packs up super tiny, fits slightly larger people
Cons:  Nearly no features, only one big pocket, super thin fabric, can feel contents
Manufacturer:   Sea to Summit
By Maggie Brandenburg ⋅ Senior Review Editor  ⋅  May 14, 2019
Our Editors independently research, test, and rate the best products. We only make money if you purchase a product through our links, and we never accept free products from manufacturers. Learn more
48
OVERALL
SCORE


RANKED
#13 of 13
  • Comfort - 25% 3.0
  • Versatility - 25% 5.0
  • Weight - 15% 10.0
  • Ease of Use - 25% 4.0
  • Durability - 10% 3.0

Our Verdict

The Sea to Summit Ultra-Sil is an impressively small, lightweight pack that minimalists are sure to love. For just a couple of extra ounces, you can clip this packed-up pack just about anywhere and be adventure-ready. A super-thin design keeps this bag reasonably comfortable and by removing nearly every extra feature, the Ultra-Sil is one of the lightest packs we've ever tested. This loss of organizational pockets and the use of thinner fabric cut into the versatility and durability of this bag a bit.

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Price $39.95 at REI
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Overall Score Sort Icon
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82
76
54
49
Star Rating
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Pros Insanely light, packs up super tiny, fits slightly larger peopleGreat features and pockets, easy to use, adjustable torso lengthGreat access to your gear, big pockets, simple yet versatileShockingly lightweight, padded shoulder straps, useful features, packs into own pocketLightweight, useful features, flap to cover cinch top, inexpensive
Cons Nearly no features, only one big pocket, super thin fabric, can feel contentsWater bottle pockets are a bit small, front stow pocket is a bit smallUnsupportive hip belt, not the most breathable back panelNo hip belt, small overall size, no back padding - can feel contentsSmall fit, hip belt not load-bearing
Bottom Line A bare-bones ultralight pack for those really dedicated to cutting out ouncesThis pack can comfortably do-it-all with excellent features, strong durability, and impressive adjustabilityA durable, versatile pack that's both easy to use and easy on your walletAn ultralight solution that doesn't cut out all the comfort and featuresA good, grab-and-go bag for smaller users, but not ideal for long hikes or heavy loads
Rating Categories Sea to Summit Ultra... Osprey Tempest 20 REI Co-op Trail 25... Osprey Ultralight S... REI Co-op Flash 18...
Comfort (25%)
3.0
9.0
7.0
3.0
4.0
Versatility (25%)
5.0
8.0
8.0
6.0
3.0
Weight (15%)
10.0
6.0
6.0
10.0
9.0
Ease of Use (25%)
4.0
9.0
8.0
5.0
6.0
Durability (10%)
3.0
8.0
9.0
4.0
3.0
Specs Sea to Summit Ultra... Osprey Tempest 20 REI Co-op Trail 25... Osprey Ultralight S... REI Co-op Flash 18...
Measured Weight 3 oz. 31 oz. 30 oz. 4 oz. 10 oz.
Volume/Capacity 20L 20L 25L 18L 18L
Back Construction Lightweight nylon AirScape backpanel; large spaced horizontal padding bars covered by large-holed mesh HDPE framesheet Lightweight nylon Lightly padded back panel
Hydration None External hydration sleeve Inner hydration sleeve None Internal hydration sleeve
Hipbelt No Yes Yes, removable No Yes, removable
Compartments 1 1 1 1 1
Rain Cover No No Yes No No
Additional pockets 0 8 5 2 1
Outside Carry Options Short daisy chain Lidlock helmet attachment, trekking pole quick-stow, large stretch front pocket, ice tool loop with bungee tie-off, side pockets, hip belt pockets, sunglasses shoulder stow, bike light loop Pole fasteners, side mesh pockets with elastic enclosure Side pocket Various small loops, one tool loop (need bungee or webbing to secure poles to daisy chain)
Whistle No Yes Yes No Yes
Key Clip No Yes No Yes Yes
Materials 30D ripstop nylon 70D x 100D nylon body, accent and bottom 420HD nylon packcloth Recycled nylon 40D Nylon ripstop Recycled nylon
Notable Features Packs into its own pocket, carabiner included Helmet attachment, trekking pole quick-stow, sunglasses quick-stow, bike light loop, shoulder strap pocket, stowable ice axe loops Ability to add REI Trail 2 Waistpack for more storage, contoured foam harness, raincover included, bottom is reinforced to be abraison resistant Packs into its own pocket Removable back padding, cinch closure cover, removable sternum strap, converts into a stuff sack

Our Analysis and Test Results

The Sea to Summit Ultra-Sil is the smallest, lightest daypack we reviewed. Sea to Summit used 30-Denier ripstop nylon and cut out all padding to make this pack weigh just 2.7 ounces.

Performance Comparison



Sea to Summit Ultra-Sil Day Pack daypack womens - if you're a fan of the ultralight, the ultra-sil might be the right...
If you're a fan of the ultralight, the Ultra-Sil might be the right pack for you.
Credit: Maggie Brandenburg

Comfort


For a pack that has literally no padding anywhere, this pack is… well, not comfortable unless you pack it right. It has no hip belt or load lifters or sternum strap, and the shoulder straps are padding-less. They do, however, have a very flat, ergonomic design that helps them hold up this bag without digging into your shoulders. And though they claim this bag can hold 250x its own weight (which would be over 40 pounds), we wouldn't recommend it for any length of time. The Ultra-Sil requires careful packing to stop from feeling every edge and corner from digging into your back. We found that this pack and other ultralight packs we tested are similar in overall comfort, though they take slightly different approaches to achieve that - rather than using some minimal padding in the shoulder straps, Sea to Summit chose a wide, ergonomic design with no padding.

Sea to Summit Ultra-Sil Day Pack daypack womens - these straps have no padding whatsoever, but their width helps...
These straps have no padding whatsoever, but their width helps distribute the weight across your shoulders.
Credit: Maggie Brandenburg

Versatility


A lot of a pack's versatility hinges on the usefulness of its features, which the Ultra-Sil is lacking a lot of. This bag is just one zippered pocket and that's about it. There's a tiny loop on top you could clip something to and three fingers-worth of daisy chain on the bottom. If you really want to get inventive (and we bet you do, you ultralight enthusiast!), the tiny stuff pouch that ends up inside the pack could double as a little pocket for your keys. It also comes with a carabiner, which can then be used to attach something to the outside of the bag while it's in use. Other ultralight models retained a few extra pockets that we think make them more useful and versatile than this one.

Sea to Summit Ultra-Sil Day Pack daypack womens - one of the few features that this bag has - three loops of daisy...
One of the few features that this bag has - three loops of daisy chain near the bottom for clipping on a bike light or attaching a whistle.
Credit: Maggie Brandenburg

Weight


It's hard to beat a bag that only weighs 2.7 ounces (carabiner included). Even the other ultralight models we tested weigh more, though barely. This weight reduction does come at the cost of those extra features and key areas of padding. But if weight is paramount, the Ultra-Sil is one of the lightest we've ever tested.

Sea to Summit Ultra-Sil Day Pack daypack womens - the ultra-sil (bottom right) is the smallest pack we reviewed.
The Ultra-Sil (bottom right) is the smallest pack we reviewed.
Credit: Maggie Brandenburg

Ease of Use


The Ultra-Sil is extremely simple. With 20 liters of internal space, it has just one large compartment that zips wide open for easy access. It's rather easy to lose one small item in just one large compartment though, as we discovered. This pack is also without any corded zipper pulls, which cuts weight, but we found ourselves missing them, as the metal zipper tabs are incredibly short.

One area in which the Ultra-Sil has a slight advantage over other ultralight models we tested, is the size of person it can accommodate. With slightly longer shoulder straps, this pack is easier for taller and larger folks to wear.

Sea to Summit Ultra-Sil Day Pack daypack womens - just one big pocket - though you could be crafty and use the stuff...
Just one big pocket - though you could be crafty and use the stuff sack as a tiny pocket too!
Credit: Maggie Brandenburg

Durability


Made of 30-Denier ripstop nylon, this pack is the thinnest we tested. Even other ultralights are thicker (though marginally so). That being said, we had no actual issues with this bag during our months of testing. That doesn't mean we'd recommend it as your primary bag to hike through a thorny ecosystem though. If you like lightweight, but don't want to sacrifice quite so much in fabric durability, you might consider some of the other lightweight simple packs we tested that only weigh a few ounces more.

Sea to Summit Ultra-Sil Day Pack daypack womens - 30d ripstop nylon is quite thin, even on the reinforced shoulder...
30D ripstop nylon is quite thin, even on the reinforced shoulder straps.
Credit: Maggie Brandenburg

Value


This pack is one of the cheapest we reviewed. For how versatile and portable it is, we think this is a great value. And hey, if you do rip an unfixable hole in that 30-Denier nylon, replacing the whole bag at this price isn't quite so painful.

Sea to Summit Ultra-Sil Day Pack daypack womens - turn any chance outing into an adventure by keeping an ultralight...
Turn any chance outing into an adventure by keeping an ultralight pack on your person.
Credit: Maggie Brandenburg

Conclusion


We appreciate the lengths Sea to Summit has gone to, to create this ultralight, super packable bag that just works. It's not one to load up with heavy or pointy objects or take on a long day out. Though we ultimately like the features included in slightly heavier ultralights just a little bit more, for an on-the-go bag, this one's pretty handy too.

Sea to Summit Ultra-Sil Day Pack daypack womens - the lightest pack we tested, the ultra-sil can come with you just...
The lightest pack we tested, the Ultra-Sil can come with you just about anywhere.
Credit: Maggie Brandenburg

Maggie Brandenburg
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