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Reactor Fleeceweight Liner
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Reactor Fleeceweight Liner delivers maximum warmth with grid-fleece Thermolite
What Our Gearhead® Experts Are Saying:
"This liner is insanely warm for the weight. The grid-pattern Thermolite fleece traps heat really well, and the shoulder zips plus drawcord footbox make it easy to regulate temps. I’ve used it to push a lighter bag deep into shoulder season—and as a standalone in warm weather. Super versatile."
We reach for the Sea to Summit Reactor Fleeceweight Liner when temperatures dip and our sleep system needs serious reinforcement. Built from hollow-core Thermolite EcoMade fibers arranged in a heat-trapping grid pattern, it’s the warmest liner in the Reactor series and the foundation of a dependable cold-weather setup. The soft fleece interior feels instantly cozy, helping us settle into camp even on frosty nights.
Thoughtful temperature-regulation features make it adaptable across seasons. Shoulder zippers allow venting without shedding warmth, and the drawcord footbox can open for airflow or close tightly on the coldest nights. Integrated design ensures seamless compatibility with Sea to Summit bags using the Free-Flow Zip system, while HeiQ Fresh technology keeps the liner feeling fresh through extended use. Warm, versatile, and remarkably comfortable, it’s the upgrade we rely on for winter camping or late-season backpacking.
Details
- Warmest Reactor liner using grid-pattern Thermolite fleece for maximum heat retention
- Hollow-core Thermolite EcoMade fibers boost insulation without excessive weight
- Shoulder zippers provide adjustable ventilation for temperature control
- Drawcord footbox opens for airflow or closes to seal in warmth
- Compatible with Sea to Summit Free-Flow Zip sleeping bags
- Bio-based HeiQ Fresh odor control keeps liner fresher on long trips
- Mummy shape enhances thermal efficiency and mobility inside any sleeping bag
- Item #STSZ0CK
- Material
- Thermolite EcoMade polyester fleece (grid-pattern)
- Shape
- mummy
- Stuff Size
- [compact] 9.8 x 3.5 x 5.5in, [standard] 9.8 x 3.5 x 5.5in
- Dimensions
- (length) [compact] 78in (198cm), [standard] 85in (216cm)
- Claimed Weight
- [compact] 13.8oz, [standard] 14.8oz
- Activity
- camping, climbing
- Manufacturer Warranty
- limited lifetime
Your Ally In Every Adventure
Since 1991, Sea to Summit has been there for every adventure. Designed to be the perfect balance of clever, packable, and light, Sea to Summit products encourage self-reliance anywhere.