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 the lightest pack we tested. This loss of organizational pockets and use of thinner fabric cuts into the versatility and durability of this bag a bit. If you want to go minimal and packable but aren't ready to give it all up for a single pocket, check out the Osprey Ultralight Stuff Pack that's just an ounce heavier and our Top Pick for an Ultralight Pack.
Sea to Summit Ultra-Sil Day Pack Review
Compare prices at 3 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
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Our Analysis and Test Results
The Sea to Summit Ultra-Sil is the smallest, lightest daypack we reviewed. Sea to Summit used 30D ripstop nylon and cut out all padding to make this pack weigh just 2.7 ounces.
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 to hold up this bag without digging into your shoulders. And though they claim this bag can hold 250x its own weight or 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 the other ultralight pack we tested, the Osprey Stuff Pack are similar in overall comfort, though they take slightly different approaches to achieve that - Osprey uses some padding in the shoulder straps while Sea to Summit chose a wide, ergonomic design.
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. The Osprey Ultralight retained a few more features, including one top pocket and one side pocket.
It's hard to beat a bag that only weighs 2.7 ounces (carabiner included). Even the Stuff Pack weighs more, at 3.8 ounces. 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 the lightest we tested.
Ease of Use
The Ultra-Sil is extremely simple. At 20 liters of capacity, it has just one large compartment that zips wide open for easy access. It's also easy to lose one small item in just one large compartment, as we discovered. This pack is also without any zipper pulls, which cuts weight, but we found ourselves missing them, as the zipper tabs are incredibly short. We much preferred the organization and usability of the Osprey Ultralight.
One thing the Ultra-Sil has a slight advantage over the Stuff Pack in, is the size of person it can accommodate. With slightly longer shoulder straps, this pack is easier for taller and larger folks to wear than the rather petite Stuff Pack.
Made of 30D ripstop nylon, this pack is the thinnest we tested. Even the Stuff Pack is thicker, with 40D ripstop nylon. 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 the REI Flash 18 that weighs just 6 ounces more.
This super lightweight bag is a great fit for ultra-lightweight enthusiasts who value lowering the ounce count about all else. If you love the ultralight life but want a few more amenities with your bag and are a smaller person, consider the Osprey Ultralight Stuff Pack instead.
At just $35, 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 30D nylon, replacing the whole bag at this price isn't quite so painful.
We appreciate the lengths Sea to Summit have 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 Osprey Ultralight Stuff Pack just a little bit more, for an on-the-go bag, this one's pretty handy too.
— Maggie Brandenburg