Elevate your outdoor sleep experience with the THERMOLITE® Reactor Extreme sleeping bag liner by Sea to Summit, designed to provide exceptional warmth in colder climates. Whether you're embarking on cold-weather adventures or seeking a versatile "stand-alone" sleeping solution for warmer nights, the Reactor Extreme has you covered. This innovative liner incorporates the power of THERMOLITE® fabric to enhance the insulating properties of your sleep system.


  • Exceptional Warmth: The Reactor Extreme liner acts as a heat-boosting layer for your sleeping bag, increasing its warmth by up to 25°F (15°C). This makes it an ideal choice for chilly environments, where staying toasty is a top priority.
  • Advanced THERMOLITE® Fabric: The hollow core fibers of the THERMOLITE® fabric are engineered to mimic the insulating properties of polar bear fur. Combined with the knitted structure, these fibers efficiently trap insulating air, ensuring that you remain comfortably warm throughout the night.
  • Superior Comfort: The Reactor Extreme features a super-soft and incredibly stretchy THERMOLITE® fabric, providing a luxurious and cozy sleep experience. Its 110g/m² fabric is notably warmer than the 80g/m² THERMOLITE® used in the standard Reactor liner, making it the perfect choice for colder conditions.
  • Technical Mummy Shape: This liner adopts a technical mummy shape with a drawstring hood, ensuring a snug fit that complements the contours of your sleeping bag. The mummy shape optimizes insulation and minimizes heat loss, resulting in a more comfortable night's sleep.
  • Easy Maintenance: Caring for your Reactor Extreme is a breeze. Simply machine wash it without the need for special detergents. Be sure to avoid fabric softeners and dryer sheets to maintain its performance.
  • Keeps Your Sleeping Bag Clean: In addition to its insulating properties, the Reactor Extreme acts as a protective barrier for your sleeping bag. It helps keep your sleeping bag clean, free from dirt, oils, and odors, extending its lifespan.
  • Ultra-Compact: The liner packs into its own Ultra-Sil stuff sack, ensuring that it takes up minimal space in your backpack.


  • Regular Mummy Dimensions: 208 cm
  • Long Mummy Dimensions: 235 x 90 cm
  • Packed Size for Both Sizes: 17 x 11.5 cm
  • Weight for Regular Mummy: 399 grams
  • Weight for Long Mummy: 422 grams

The Sea to Summit Reactor Extreme THERMOLITE Liner is your go-to solution for boosting warmth, extending the usability of your sleeping bag, and ensuring a cozy night's rest in colder climates. Whether used as an additional layer for frigid nights or a stand-alone sleep option in warmer weather, this innovative liner is an indispensable addition to your outdoor gear collection.


Barcode # 9327868022304
Brand Sea to Summit

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