Adventure Medical Kits # 1 selling survival item for the past five years! The Adventure Medical Kits SOL Thermal Bivvy is a year round bivvy sack that is ideal as a light weight replacement for your sleeping bag when temperatures are above 50F/9C and an excellent emergency survival shelter for winter time activities. The SOL Thermal Bivvy reflects 80% of radiated body heat and the Thermo-Lite non-woven fabric is waterproof and windproof. (Formerly the Thermo-Lite 2.0 Bivvy)