Elevate your cold-weather sleep system with the Sea to Summit Reactor Extreme Sleeping Bag Liner, the ultimate solution for enhancing warmth and comfort on chilly nights outdoors. Engineered with Thermolite Pro fabric, this liner incorporates infrared-absorbing ceramic pigments that reflect your body heat back to you, increasing the thermal efficiency of your sleeping bag setup-perfect for alpine conditions, shoulder-season backpacking, or lightweight winter camping. The stretch-knit construction delivers a soft, wicking, and body-hugging fit that moves with you for unrestricted comfort through the night. It works seamlessly with any sleeping bag and can even be used on its own in warmer conditions. A drawcord-adjustable footbox provides additional airflow control and allows you to walk around camp while wearing the liner-adding convenience without sacrificing insulation. Whether you&';re looking to extend the life and warmth of your sleeping bag or just need a reliable, packable layer for added heat, the Reactor Extreme is a lightweight, compact essential for cold-weather adventurers. Features: Thermolite Pro Fabric with Ceramic Infrared TechnologyReflects body heat to enhance thermal performance in cold environments. Adds Significant Warmth to Sleeping BagsBoosts insulation by up to 25AdegF (varies by conditions and bag). Soft, Stretch-Knit ConstructionComfortable, wicking, and non-restrictive-ideal for restless sleepers. Versatile Drawcord FootboxOffers ventilation and allows walking around camp while wearing the liner. Compact & LightweightPacks down small, making it easy to carry in any backpacking setup. Extends Sleeping Bag LifeKeeps your sleeping bag cleaner, reducing the need for frequent washes. Universal FitCompatible with most sleeping bags and usable as a standalone layer in warm climates.