The Thermolite Reactor Extreme sleeping bag liner is the warmest liner offered by Sea to Summit.  It can increase your sleeping bag warmth by up to 25 degrees.  If you are expecting a wide variety of temperatures on a trip, or just want to make extra-sure you stay warm, this liner is a great choice.


Best Use: Backpacking, Camping, Winter Camping


MSRP:  $70.00


From Sea to Summit:


The THERMOLITE® Reactor™ Extreme is the warmest backpacking knit sleeping bag liner we offer. The hollow fiber threads work just like the hollow fur of a polar bear in that they trap heat effectively. When the mercury drops you'll appreciate the mummy shape and drawcord hood with mini cord lock attached. Depending on your environment and sleep conditions, this liner can increase your sleeping bag warmth by up to 25F. 


  • Adds up to 25°F / 14°C of warmth to a sleeping bag
  • Lighter weight, more packable than fleece
  • Mummy shape with a box foot
  • Drawcord hood with mini cord lock
  • Packs into its own Ultra-Sil™ stuff sack

Sea to Summit Thermolite Reactor Extreme Sleeping Bag Liner

  • Weight:  14oz

    Pack Volume:  3in x 5in


    If you are unhappy with your Gear Shack experience for any reason, please reach out to us. We want the opportunity to make things right - which may include issuing a complete refund.


    We understand that plans can change. If you cancel two weeks or more before the start of your rental period, we will provide a full refund. Any cancellations made within two weeks are not eligible for a refund.