Sea to Summit Thermolite Reactor Fleece Liner

The Thermolite Reactor Fleece is designed to add up to 25 degrees Fahrenheit of warmth to your existing sleep system. It uses hollow-core fibers and infrared-absorbing ceramic pigments to trap and reflect your body heat effectively.

Yes, it functions well as a standalone sleeping bag during warmer nights. The mummy shape and stretch-knit fabric make it comfortable for sleeping, while the shoulder openings and drawcord footbox allow you to vent heat if you get too warm.

Not at all. The fabric is a stretch-knit, which allows for natural movement throughout the night. Additionally, the shoulder openings let you easily slide your arms out, preventing that confined feeling often associated with mummy-style liners.

The drawcord footbox allows you to cinch the bottom tight to seal in warmth or open it up completely for ventilation. It is a practical feature if you tend to get hot feet or need to walk around camp while still wearing your liner.

It is designed with a standard mummy shape that fits most traditional mummy sleeping bags. However, if you use a quilt or a non-mummy bag, the fit may be less precise, though it will still provide the intended thermal benefits.

The liner weighs 13.8 ounces. While it adds a bit of weight to your pack, it packs down compactly, making it a manageable trade-off for the significant boost in warmth it provides on cold-weather trips.