A whopping 10cm depth with next to four season levels of warmth. Due to the way in which it’s constructed it also packs down to an impressively small size. The new Winglock valves - which are due to roll out throughout the whole Thermarest range - provide an inflate and deflate mode so you don’t lose any extra air (unless you want to). It is also completely replaceable. It also comes with the MicroPump, which aids inflation and weighs in at a minimal 65g.