The THERMOLITE® Reactor™ Extreme liner is Sea to Summit’s warmest knitted sleeping bag liner. If your adventures take you to colder climates, the Reactor Extreme will add plenty of warmth to a sleeping bag. Plus in warmer weather, it can be used as a ‘stand alone’ sleeping bag. The hollow core fibers of the THERMOLITE® fabric work like a polar bear's fur and, along with the knitted structure, trap plenty of insulating air. Super soft and amazingly stretchy, the Reactor Extreme uses a heavier version of THERMOLITE®  to provide extra warmth for an incredibly comfortable night’s sleep. Use one to build your cooler-weather sleep system and to help keep your sleeping bag clean too.

• Traps insulating air to increase warmth of a sleeping bag by up to 25°F / 15°C
• Stretchy, Thermolite® fabric is incredibly comfortable.
• 110g/m² fabric is warmer than the 80g/m² Thermolite® used in the standard Reactor.
• Technical mummy-shape with drawstring hood.
• Easy care – machine wash with no special soap needed. Avoid fabric softeners and dryer sheets.
• Keeps sleeping bag clean.
• Packs into its own Ultra-Sil stuff sack.