Comfort is not ‘one size fits all’, which is why the Boost 650 empowers you to customize its shape to find your perfect balance of space and warmth. As a spacious semi-rectangular sleeping bag the Boost provides all the room you need to side sleep, shift about, spread out and relax. The semi-rectangular shape gives you considerably more internal space than a mummy bag — you’ll feel unrestricted and free to sleep in whatever position you want all night long. But more space demands more body heat to warm it up and cold isn’t comfortable. That’s where WarmZip comes in. Zipping up the WarmZip center zipper transforms the shape of the Boost 650 from a semi-rectangular bag to a thermally efficient mummy bag. It pulls the 650-fill down around your body and reduces the amount of space your body needs to heat. WarmZip gives you the power to add up to 10F/6C to the Boost’s temperature rating. Standard Therm-a-Rest features like a puffy draft collar, a draft tube along the entry zipper line and a cinchable hood round out the Boost’s bliss-inducing comfort. The Boost 650 was built to backpack—we dialed in the materials and design to make it light, packable and high-performing in variable backcountry conditions. Zoned Insulation places the 650-fill hydrophobic down in key warmth-retention areas (on top, around your core and shoulders) and reduces it where it’s less efficient (on the bottom), allowing the Boost to create more warmth with less down. The shell and liner are made of 100%-recycled nylon that was handpicked for its light weight and super-soft feel. The PFAS-free DWR coating and the hydrophobic down keep the Boost warm and comfy even in wet weather.

• Boost 650: Ultra-comfy warmer weather backpacking sleeping bag with adjustable shape and warmth
  
• Customizable Comfort: Enjoy the spacious freedom of the semi-rectangular bag or the cozy warmth of a mummy bag
  
• WarmZip™ Tech: Patent-pending center zipper design zips up to reduce the bag’s internal space and tuck insulation around the sleeper to boost warmth 
  
• Multi-Use Arm Holes: Reach the WarmZip, read a book, play cards or simply ventilate — do it all while tucked into your sleeping bag for elevated livability
  
• Plush & Puffy: 650-fill RDS-certified hydrophobic down is allocated to key areas with Zoned Insulation for refined heat efficiency and maximum coziness
  
• Eco-Conscious Materials: Shell and liner are made of GRS-certified 100% recycled, soft-to-the-touch nylon and coated with PFAS-free water repellent
  
• Additional Features: YKK anti-snag zippers, cinchable hood, zipper draft tube, puffed draft collar, and a two-way entry zipper
  
• Includes Boost 650, Compression Sack, and Storage Sack
  
• Shell fabric: 20D 100% Recycled Nylon Rip Stop
  
• Lining fabric: 20D 100% Recycled Nylon Rip Stop
  
• Fill material: 650 Fill Duck PFAS Free Hydrophobic Down, RDS
• Fill weight: 1.7 lb
  
• EN Comfort (C): 0 C
  
• EN Comfort (F): 32 F
  
• EN Limit (C): -6 C
  
• EN Limit (F): 20 F
  
• EN Extreme (F): -9 F
  
• EN Extreme (C): -23 C
  
• Zipper side: Left
  
• Length: 80 in
  
• Fits: 72 in
  
• Girth Shoulder: 64 in
  
• Girth Hip: 60 in
  
• Girth Foot box: 61 in
  
• Packed dimension: 12.5 in x 7.5 in
  
• Weight: 2 lb 11 oz

• EN Rating

  32 F (Comfort) / 20 F (Limit) / -9 F (Extreme)

• Fill Type

  650 Hydrophobic Duck Down

• Stuff Size

  12.5 x 7.5 in

• Total Weight

  2 lb 11 oz