Sea to Summit Thermolite Reactor Extreme Sleeping Bag Liner

Weighs 386g
Code: OC1529
  • £53.99
  • (FREE Delivery on orders over £15)
  • RRP £59.99
Item out of Stock | Usually dispatched within 24 hours

Increases sleeping bag performance by up to 15°C (25°F) with super-insulating 110g/m² Thermolite fabric. Spacious design allows for a comfortable night’s sleep even when the mercury plummets.

Sea to Summit says:

The Thermolite® Reactor Extreme increases sleeping bag performance by up to 15°C with its super insulating 110g/m² Thermolite® fabric. The spacious design is slightly tapered from head to foot to reduce weight and increase thermal efficiency, and the drawcord hood can be cinched down for extra warmth when required. This knit fabric also has serious stretch to it, making the Reactor Extreme the ideal liner for the restless sleeper.

The liner is made from Du Pont Thermalite fabric which is a hollow core fibre that provides maximum insulation for weight. If you want a liner to keep your bag clean then this must be a consideration as it offers an insulation upgrade at the same time.

With the stretchy knit fabric that moves with you and a drawcord hood the Thermolite Reactor Extreme liner is perfect for wrigglers and rollers or anyone who needs some extra warmth. 

Ideal as part of a cold climate sleep system or standalone bag in warm weather.

- Reviewed by Ultralight Outdoor Gear

  • Adds up to 15°C / 25°F warmth to a sleeping bag
  • Super-insulative 110g/m2 THERMOLITE throughout for extra warmth
  • Mummy shape with a box foot
  • Draw cord hood with mini cord lock
  • Extends life of sleeping bags by keeping them clean
  • Contrasting colour along the top edge makes it easier to find the opening
  • Packs into its own Ultra-Sil™ stuff sack
  • Easy care, machine washable


  • Weight: 386g
  • Length: 210cm / 6 ft 11in
  • Width: 90cm / 35in
Showing our 2 Sea to Summit Thermolite Reactor Extreme Sleeping Bag Liner reviews with an average rating of Excellent. Would you like to write a review?
Review Summary - 5 out of 5 based on 2 ratings.
May 3, 2019 | HK
Super comfortable and warm liner

Used this liner for few nights now, on temperatures around 0°C. I'm a really "coldsleeper" and this liner definitely helped me to sleep nice and warm in my Fjällraven Abisko 3 season sleeping bag. + This liner is super comfortable + It definitely adds some warm to your sleeping system, especially if you use the hood although I'm not sure that it could add a warmth it stated on the label and it'll definitely not turn a bad sleeping bag to a good one. But it's still a new 'must have' item in my bag. Would i purchased it again? Definitely YES! A really good product.

Ultralight Outdoor Gear Limited
January 27, 2017 | Archie
Warm and comfy

Went hiking after christmas, and i used this with 3-season fjällräven sleeping bag. It was very warm, alltough it was only -7c at night.

Ultralight Outdoor Gear Limited