Sea to Summit Reactor Midweight Liner

The Sea to Summit Reactor Midweight Liner is a versatile thermal fleece liner designed to enhance warmth and flexibility within any sleep system. Constructed from stretch-knit fleece with integrated armholes, it allows unrestricted movement for side sleepers and active sleepers, while fitting neatly inside any sleeping bag. Thermolite® Pro fibres with Far Infrared (FIR) technology and hollow-core construction efficiently trap and reflect body heat, increasing warmth by up to 6°C / 11°F without adding unnecessary bulk. Quick-drying and treated with HeiQ Fresh odour control, it is easy to maintain and helps extend the lifespan of your sleeping bag by reducing wash frequency and preserving insulation loft.

Features: 
- 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