The Sea to Summit Reactor Thermolite Sleeping Bag Liner is a bestselling, ultra-stretchy technical liner designed to boost the warmth of your existing sleep system while keeping your sleeping bag clean.

Unique Performance Highlights

• Infrared Thermal Boost: Built with Thermolite Pro fabric, which blends hollow-core fibers with permanent ceramic pigments. These specialized pigments absorb your body's radiating heat and reflect it back to you, adding up to 14°F / 8°C of extra warmth to your bag.
• Incredible 4-Way Stretch: Unlike stiff silk or cotton sheets, the stretch-knit fabric moves completely with you. This allows unhindered toss-and-turn movement and ensures it expands comfortably to fit sleeping bags of any shape.
• Camp-Ready Versatility: Modern iterations feature specialized shoulder snap-openings so you can slip your arms out to read or drink coffee while staying cocooned. Models with a drawcord footbox let you hitch the liner up around your waist to safely walk around camp or manage nighttime bathroom breaks.
• Odour Control & Hygiene: Treated with HeiQ Fresh FFL, a bio-based, biocide-free silver alternative that permanently neutralizes body odours. It acts as a barrier to skin oils, drastically reducing how often you need to wash your main, expensive sleeping bag.

Specifications at a Glance

• Added Warmth: Up to 14°F / 8°C thermal boost.
• Weight: Exceptionally light at 8.7 oz (248 grams).
• Dimensions: 82 inches (208 cm) long; fits sleepers up to 6'6" (198 cm) in the standard mummy profile.
• Packed Size: Compresses down tiny into its own Ultra-Sil stuff sack, measuring just 5.75 x 4 inches (smaller than a water bottle).
• Sustainability: Constructed using 50% recycled Thermolite EcoMade fibers sourced from textile waste.