Sea to Summit Reactor Midweight Liner

The Sea to Summit Reactor Midweight Liner is a dependable way to add noticeable warmth to your sleeping bag without carrying extra weight. Made from stretchy fleece with built-in armholes, it lets you move comfortably through the night, whether you’re a side sleeper or constantly turning over. Thermolite® Pro with heat-reflective FIR technology helps trap body warmth, adding up to 6°C when used as part of your sleep system. Quick-drying and treated with HeiQ Fresh to control odours, it’s easy to clean and helps keep your main sleeping bag fresher for longer.

Details: 
- Freedom to Move: Stretch-knit construction and armholes allow unrestricted movement in any sleep position.
- Thermal Boost: Thermolite® Pro with FIR and hollow-core fibres traps and reflects heat—adds up to 6 °C | 11 °F to your system.
- Easy to Clean: Quick-drying fabric with HeiQ Fresh odour control for extended freshness on multi-day trips.
- Bag Compatibility: Fits any sleeping bag and snaps into Sea to Summit bags for easier entry/exit.
- Extend Bag Lifespan: Reduces need for frequent washing, maintaining insulation loft over time.
- Adventure-Ready: Ideal for backpacking, hut trips, bikepacking, and travel where warmth and hygiene matter.

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: 198cm

Long: 
Fits up to height: 198cm
Weight: 355g