The Therm-a-Rest ProLite Apex sleeping pad features a StrataCore construction that offers the best warmth-to-weight ratio (630 g in regular size) among self-inflating mats. Inside the sleeping pad, there is a continuous layer of thermal foam, integrated between alternating air and foam channels. The combination of the highly expansive and highly insulating foam with weight-saving air channels makes the ProLite Apex the warmest ProLite pad that Therm-a-Rest has ever designed. After the foam expands, the sleeping pad can be adjusted to individual firmness with just a few additional breaths. The WingLock valve is very helpful for this, as it operates intuitively and prevents unwanted air escape during inflation. Another advantage is the extremely compact pack size for a 3-season pad with a comfortable thickness of 5 cm. This ensures restful sleep even in frosty outdoor temperatures. Moreover, the small pack size of the Therm-a-Rest ProLite Apex leaves more room for chocolate in your backpack during winter trips.