Featuring grippy silicone traction prints, a new valve that features deflation assistance, and a self-inflating foam core, the Ultralight SI Mat from Sea to Summit promises unique features in a lightweight, packable design. How did it hold up in our testing? This is my review.
The Sea to Summit Ultralight SI mat is a 1″ thick self inflating mattress, meaning the core is a lightweight foam, drilled out to reduce weight, and paired with a 30D polyester shell to trap air inside. This foam core naturally expands back to it’s original shape when unrolled, which creates a vacuum and allows it to inflate itself by pulling in air. The included valve is a clever multi-function system that allows for one way inflation , quick dump deflation, and allows for small adjustments to the stiffness of the pad via a small deflate button that allows just a bit of air to escape at a time. The regular sized pad tested here comes in at 72″ x 20″ x 1″, weighs 1 lb 3 oz and retails for $89.95.
What I liked
At just 1 lbs 3 oz, the mat is light enough for any backpacking trip. It packs down to a very reasonable size at roughly 11″ x 6″ when in the storage sack. Folding it into flat layers instead of a roll allows it to slide nicely into my backpack, taking up minimal space. It can even be worked into folds around my sleeping bag, filling in the gaps that my compression sack usually creates, minimizing wasted pack space. I’ve also found that I can roll it up and stuff it back into it’s included sack to store it out of the way without having any compression issues when unpacking it. This makes storage easy.
The SI Mat manages to impress when it comes to durability. The 30D polyester shell holds up great to prolonged use, easily tolerating zippers, boots and the like when moving in and out on top of it. So far, I’ve had no punctures, fraying, or anything damage of any kind to the valves or seams. It also cleans up easily, washing up nicely with just a damp towel.
Overall, it’s a fairly comfortable sleeping mat. It can be inflated hard to provide some of the best support I’ve found in a mat, or softened enough to provide some cushioning as you sink into it’s 1″ thickness, absorbing the contours of the chest or spine. It has an overall stiffer feel than most pads I’ve tested, and some people will prefer this to a soft, squishy pad. When stomach or back sleeping, it works quite well, providing a good balance between firmness and softness thanks to the internal foam, which does a great job of distributing pressure and providing relief from tension on joints.
Being a foam filled pad, the warmth from the insulation can be instantly felt. Despite having a relatively low R-value of 2.6 (for a SI pad), I’ve found that it does a great job of providingng warmth all the way down to freezing temperatures. this makes it a great candidate for quilts or sleeping bags that ditch the insulation that would otherwise flatten against the pad, shaving a lot of weight. I haven’t tested it below freezing yet, but I’ll report back when I get the chance.
It’s compatible with Sea to Summit’s own Jet Stream Pump Sack, which is simply delightful. It pops onto the one-way valve, then acts like a bit of an accordion, bobbing up and down to inflate the pad. It takes a minute, but overall works great and is way better than blowing or topping up a pad by mouth. It’s also far more sanitary.
The pad has small silicone imprints along the surface, providing extra grip to help prevent it from slipping around inside a tent, or underneath a sleeping bag. This small change really helps when sleeping on a slight incline, as the pad isn’t going to work its way to the corners of the tent, which can be frustrating. They can’t be felt during use, even while using a bottomless quilt, and so far they’ve held up great and have maintained their slightly tacky feel despite lots of use.
What I didn’t like
While nice for stomach and back sleeping, the fairly minimalistic pad doesn’t do a great job of providing support for side sleeping, mostly due to the limited thickness. The firm, at times rigid, feeling foam doesn’t provide the amount of support or compression needed to fully absorb the shape of wide, thick shoulders. This makes it less than ideal for anyone who sleeps directly on their side. The pad can be softened by releasing some air, but it’s never quite enough to compensate. Sea to Summit does offer thicker variations of this pad, albeit at a slight weight penalty. This is likely a better candidate for those who need the extra depth and padding required for a proper side sleep.
Packing this pad back into its included stuff sack is in itself an adventure. The stuff sack is absolutely minimal, meaning making use of it requires a little dedication. The pad comes with a nifty twisting valve that allows for one way deflation, which helps during the compression stage of things, but ultimately it’s not enough to make the tiny sack any more viable. I’ve spent as long as five minutes feverishly rolling, compressing and shoving to try to get the pad back in it’s sack, only to eventually realize it’s just far easier and more convenient to fold it up flat and stuff it into my pack that way. It’s not impossible to get back in, but it’s certainly close enough that it’s not really worth the effort, at least for me. On the plus size, if you do manage to get it inside, it’s going to be at a nice, compact size that will take up minimal space, and that’s likely the point.
In the end, I found myself mostly liking the Ultralight SI pad from Sea to Summit. It’s light enough that’ it’s easily justifiable on any length backpacking trip, and it’s appropriately sized so that it fits great in a small, lightweight tent without running up against the walls. It packs down to a compact size that handily slides into the crevices often formed by other gear. It’s built great and will ultimately prove reliable, season after season. It’s even fairly comfortable and warm, if you’re primarily a back or stomach sleeper. If you’re a side sleeper or need lots of cushion, I would suggest a squishier option like the impressive Comfort Light. Otherwise, this is a good option for those looking for a firm, compact,, lightweight sleeping surface.
Recommended for some
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I want to extend a huge thanks to Sea to Summit for providing this product for review. We couldn’t do it without their help. Our full disclosure can be found here.
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