Reactor Midweight Liner

The cheapest way to make a sleeping bag warmer. A Reactor Midweight adds up to 11°F to your sleep system for about 12 ounces, which is a far better trade than buying a warmer bag, and it lets one bag cover a wider season.

The fabric is Thermolite Pro: hollow-core fibers plus infrared-reflective ceramic pigment, so it traps your own heat rather than just adding a layer of cloth. Cut with a technical mummy shape, a fitted hood and shaped arm openings, so it moves with you instead of twisting into a rope by 2am. Snap connectors at the shoulders pair it with Sea to Summit bags.

The other reason to own one: it takes the wear. Wash the liner instead of the bag and your down lasts years longer.

Specs

• Adds up to 6°C / 11°F to your sleep system
• Short: 330 g / 11.6 oz · 70 x 31 in · fits to 5'7"
• Regular: 350 g / 12.3 oz · 76 x 31 in · fits to 6'1"
• Long: 365 g / 12.9 oz · 78 x 31 in · fits to 6'6"
• Packed size: 7 x 5 x 5 in, all sizes
• 100% post-consumer recycled polyester, bluesign approved
• HeiQ Fresh odor control
• Shoulder snap connectors, machine washable