Sea to Summit Reactor Fleeceweight Liner

The Sea to Summit Reactor Fleeceweight Liner is designed to give your sleep system a serious warmth upgrade in cold conditions. Stretch Thermolite® Fleece and integrated armholes provide comfort and freedom of movement, while the grid-fleece design with hollow-core fibers locks in heat and boosts warmth by up to 8°C / 14°F. It packs down smaller than a full sleeping bag upgrade and dries quickly after washing. With odor control treatment and snap-in compatibility for Sea to Summit bags, it’s a smart way to stay warmer and protect your gear on extended trips.

Details: 
- Freedom to Move: Thermolite® Fleece fabric and armholes allow unrestricted movement in any sleep position.
- Thermal Boost: Grid-fleece with hollow-core fibres traps and reflects heat—adds up to 8 °C | 14 °F warmth.
- Bag Compatibility: Fits any sleeping bag; snaps into Sea to Summit bags for secure placement and easy entry/exit.
- Extend Bag Lifespan: Reduces washing frequency to maintain insulation loft and long-term performance.
- Easy to Clean: Quick-drying fabric with HeiQ Fresh odour control stays fresher on multi-day trips.
- Ideal for cold-weather backpacking, hut trips, and winter bivvies where extra warmth matters.

Technical Specifications:

- Added Warmth
Up to 6°C
- Best Use
Backpacking, Camping & Winter Camping
- Comes With
Ultra-Sil stuff sack
- Material(s)
Thermolite Pro & Thermolite EcoMade
- Shape
Mummy

- Regular: 
Fits up to height: 185cm
Weight: 400g
- Long: 
Fits up to height: 198cm
Weight: 420g