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    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.


    • Stretchy, Thermolite® fabric is incredibly comfortable
    • 110g/m² fabric is warmer than the 80g/m² Thermolite® used in the standard Reactor
    • Works like your favorite cold-weather base layer to trap insulating air and increase warmth
    • Easy care – no special soap is needed
    • Significantly improves the thermal performance of your sleeping bag
    • Comfortable stretchy fabric
    • Keeps sleeping bag clean
    • Machine wash and air dry - Avoid fabric softeners & dryer sheets to maintain wicking performance
    • Packs into its own Ultra-Sil™stuff sack


    Easy to wash and helps to keep your sleeping bag cleaner for longer.
    Regular Mummy
    Dimensions - 82"
    Stuff Sack Size - 6.5 x 4.5"
    Weight - 14oz
    Long Mummy
    Dimensions - 92.5"
    Stuff Sack Size - 6.5 x 4.5"
    Weight - 14.9oz