What is the Sea to Summit Thermal Boost Liner Reactor Fleeceweight?
The Reactor Fleeceweight Liner is excellent for campers and trekkers facing colder conditions. As the warmest option in the Reactor range, it uses advanced fleece technology to provide extra insulation, comfort, and hygiene while extending the life of your sleeping bag. Whether camping in the mountains or tackling long, cold-weather expeditions, it delivers reliable warmth and performance.
What is it made of?
Thermolite Grid Fleece
The Fleeceweight features Thermolite hollow-core fibres woven into a soft grid fleece construction. This traps and reflects body heat, boosting insulation while remaining breathable and lightweight. Integrated into a sleep system, it can add up to 8°C | 14°F of warmth, making it ideal for cold-weather use.
Thermolite EcoMade All Season
Made with recycled fibres, Thermolite EcoMade All Season reduces environmental impact while maintaining excellent thermal efficiency. The added recycled polyester content strengthens the liner’s sustainability credentials without compromising performance.
HeiQ Fresh Odour Control
HeiQ Fresh odour-control treatment prevents unwanted odour build-up, keeping the liner fresher for longer on extended trips where washing opportunities are limited.
Bluesign Approved & Recycled Blended Claim Standard
The liner meets strict Bluesign standards for responsible water, energy, and chemical use, ensuring environmentally conscious production. It is also certified under the Recycled Blended Claim Standard (RCS), verifying genuine, traceable recycled content.
What are its features?
Freedom to Move
The stretch-knit fleece and armholes adapt to your sleeping style, providing unrestricted comfort whether you toss, turn, or sprawl.
Arm Openings with Zips
Zipped armholes allow for ventilation, free-arm mobility, or seamless integration with Sea to Summit sleeping bags for easier entry and exit.
Technical Hood
A snug hood adds insulation around your head and neck, helping lock in heat on freezing nights.
Boosts Sleep System Warmth
Adding up to 8°C | 14°F, the Fleeceweight liner provides the highest warmth boost in the Reactor range.
Extends Sleeping Bag Lifespan
By acting as a protective barrier against sweat, dirt, and oils, the liner reduces how often your sleeping bag needs washing—helping maintain loft and extend its lifespan.
Easy to Clean
The liner is lightweight, quick-drying, and simple to wash, keeping your sleep system fresh with minimal effort.
Features:
- Thermolite grid fleece construction
- Arm openings with zips
- Technical hood
- Free Flow compatible armholes
- HeiQ Fresh odour control
- Thermolite EcoMade All Season fibres
- Recycled polyester content
- Fits any sleeping bag
- Easy to clean and quick-drying
- Bluesign Approved, Recycled Blended Claim Standard