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.

Learn more about which liner is right for you .

DOES THE REACTOR EXTREME LINER...?

• Add 25°F / 15°C to any sleeping bag? Not necessarily. There are a lot of factors involved in the thermal performance of a sleep system, starting with the insulation value of your sleeping pad. Read more .
• Work for backpacking? For most backpackers. The Reactor Extreme weighs 13.9 ozs – a reasonable trade off in weight/thermal performance for occasional cold-weather backpackers. Weight-conscious performance users may opt for a Spark Sp 0 / Flame Fm 0.
• Need special care when being washed? No! The Reactor Extreme can be washed in a washing machine with normal supermarket laundry ‘soap’; just avoid fabric softeners as they will reduce the wicking performance of the fabric. You can dry it in a dryer, use cool or low heat.