The Bottom Line: A superbly versatile mat that is warm and more than lightweight enough to fall under the ultralight category. The SynMat HL Winter performed in winter camping down to -22 degrees, both in tents and in snow shelters, and lightweight summer backpacking trips alike.
Exped makes some of the best mats in the business. They are the most comfortable without compromising weight or warmth. In comparison to Therm-A-Rest Xtherms, Big Agnes, and a few others, they are consistently my go-to for the soft microfiber material, the easy inflation system, and low pack weight.
The Winterlite M's larger side baffles prevented me from slipping off while asleep. It's a very thick mat, which means my sharp, bony hips never go through to the ground when I sleep. The soft microfiber face is really quite nice when you forget your pillow. It is quieter to the touch compared to other mats on the market, which sensitive sleepers will appreciate. It packs up the size of a Nalgene, and its weight is beneath the 500-gram threshold for ultralight insulated mats. For such a comfortable mat, it's incredible how small and light it is.
Inflation is incredibly easy. The large Schnozzle Bag that comes with this mat acts as a bellows. A self-sealing valve insures that air only goes one way. You shake the Schnozzel Pump Bag full of air then knead the air into the mat. It rarely takes more than three pushes. It is faster than any other system I have used. This pump now also works on other sleeping pads.
The SynMat has two major downsides. First, deflation is a bit of a pain. You have to knead the air back out using a tab to jam open the self-sealing valve. Second, the sleeping pad also has a narrow foot taper. Unlike the Therm-A-Rest mummy shape, the Exped is very narrow at the feet. I frequently find my feet sliding off the end.
Unfortunately, the warranty process may be lacking. One of the valves snapped while inflating it on a trip, leaving a gigantic baffle. This made sleeping rather awkward. After an effort to replace the mat via the warranty, the store eventually offered to replace the mat for me. Sadly they were out of the mediums, so they gave me a wide. Much larger and heavier, this wasn't my ideal scenario. Apparently brittle valves are no longer a concern. It's worth noting that the wider mat is much more comfortable and my feet no longer slide off. For winter trips, the extra width is a boon that adds a little warmth.
If you're a sensitive sleeper or a soft face is important for lightweight winter camping, this mat is ideal. The medium is a little thin in the feet if you're an active sleeper, but it is more than adequate for most winter conditions. Easy inflation is great, and cumbersome deflation is something you learn to live with. If you need instant pack-ups, a Z-Lite might be a better buy.