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Reactor Extreme Liner (adds up to 25°F)
$74.95 $56.21

Reactor Extreme Liner (adds up to 25°F)

$74.95 $56.21
Perfect for cold weather backpacking+ View tech specs
  • Size
  • Shape

BEST USE: Backpacking & Camping

WEIGHT: 14 oz | 399 g

LENGTH: 6 ft 10 in | 210 cm

PACKED SIZE: 6.5 x 4.5 in | 17 x 11.5 cm

Shipping & Returns

Our warehouse is actively shipping orders from 8am to 1pm MST Monday through Friday. Most orders ship in one business day, but the transit time can take up to 7 days, depending on your distance from Boulder, Colorado.

2nd Day and Next Day Air orders will ship same day if placed by 1pm MST, Monday-Friday (except holidays).

All orders are eligible for fast and easy returns within 60 days of purchase.

For more details, please check out our Help Center

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Reactor Extreme Liner (adds up to 25°F)
Reactor Extreme Liner (adds up to 25°F)
$74.95 $56.21
Description || Reactor Extreme Liner (adds up to 25°F)


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. Plus in warmer weather, it can be used as a ‘stand alone’ sleeping bag. The hollow core fibers of the THERMOLITE® fabric work like a polar bear's fur and, along with the knitted structure, trap 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 keep your sleeping bag clean too.

Design Details

Technical Features


Tech specs

  • Added Warmth
    Up to 25°F / 14°C
  • Best Use
    Backpacking, Camping & Winter Camping
  • Comes With
    Ultra-Sil stuff sack
  • Material(s)
    Thermolite polyester fabric
  • Shape
Regular MummyLong Mummy

Frequently Asked questions

Does this sleeping bag liner fit regular and wide sleeping bags?

This liner is made with durable stretch fabric so it can fit in any sleeping bag shape and you won't even notice.

Does the sleeping bag liner have a zipper?

No. In order to keep this sleeping bag liner at a minimal weight and packed size we did not include a zipper.

Is the sleeping bag liner machine-washable?

Yes! This sleeping bag liner is machine-washable for ease and convenience. You can wash your liner with laundry detergent and machine dry, using cool or low heat. Steer clear of fabric softeners, though, since they tend to reduce wicking performance of the fabric. 

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