Sea to Summit Reactor Midweight Sleeping Bag Liner Regular Beluga

The Sea to Summit Reactor Midweight Fleece Liner is the versatile, go-to thermal boost for every adventure. Built from stretch-knit fleece with integrated armholes, it delivers exceptional freedom of movement whether you’re a side sleeper or a restless tosser-and-turner. It fits inside any sleeping bag and snaps into Sea to Summit bags for easier entry and exit.

Powered by Thermolite® Pro with Far Infrared (FIR) technology and hollow-core fibres, the Reactor Midweight efficiently traps and reflects body heat to increase warmth without unnecessary bulk—adding up to 6°C | 11°F when used as part of a sleep system.

Unlike a full sleeping bag, the liner is easy to clean and quick-drying. The HeiQ Fresh odour-control treatment helps it stay fresh during extended trips, while reducing how often you need to wash your sleeping bag—helping maintain loft and extend its usable life.

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.

Specifications - Regular Size

• 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
• Fits up to height: 185cm
• Weight: 350g