Sea to Summit

Sea to Summit - Reactor Extreme Sleeping Bag Liner

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  • Regular price $89.95

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. In warmer weather, it can be used a ‘stand alone’ sleeping bag. The hollow core fibers of the THERMOLITE® fabric work like hollow polar bear or caribou fur – along with the knitted structure, this traps 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 to keep your sleeping bag clean, too.


  •  Constructed of insulating Thermolite® fabric, a hollow-core, breathable fiber that provides extraordinary warmth for its weight
  •  Adds up to 25°F of warmth to a sleeping bag; can also be used as a summer ultralight sleeping bag
  •  Liner helps keep the inside of your bag clean, saving it from the wear and tear of washings
  •  Drawcord hood with mini cordlock cinches around face to hold warmth in
  •  Mummy shaped liner features a 3D footbox providing plenty of room for feet
  •  Comes with a lightweight Ultra-Sil™ stuff sack


Technical Specs

Best Use


Sleeping Bag Shape


Added Warmth (F)

Up to 25 degrees

Added Warmth (C)

Up to 14 degrees

Stuff Sack Size

3 x 5 inches




84 x 36 inches


14 ounces