Sea To Summit Thermolite Reactor Extreme Liner -Increases sleeping bag performance by up to 25 F (14 C) with super-insulating 110g/m Thermolite fabric. Thermolite is a hollow core fiber that provides extraordinary warmth for its weight and remains extremely breathable. Spacious design allows for a comfortable night's sleep, even when the mercury plummets. Perfect for extending the season of your sleeping bag. Size: 84" x 36" Weight: 14 ozTemp Rating: Up to 25° FMummy shape with a box footDraw cord hood with mini cord lockPacks into its own Ultra-Sil stuff sack