The Thermarest ProLite Apex brings packable performance and legendary support. The self-inflating foam measures 2 inches (5 cm) and features the StrataCore construction, a design that provides the best warmth-to-weight ratio of any self-inflating foam construction. The ProLite Apex 3.8 R-value allows adventurers to stave off the cold during three-season pursuits. The packable self-inflating pad features the high-performance WingLock valve, which has three-times the airflow rate of the classic valve thanks to a larger opening and one-way inflation. ProLite Apex L Sleeping Mat