Skip to content
Orders over $99 Ship Free + Free In-Store Pickup
Orders over $99 Ship Free + Free In-Store Pickup

Spark Ultralight Sleeping Bag 40º

Sold out
Color: Light Grey / Yellow

Notify me when back in stock

Enginereed to keep you warm at the lightest weight and smallest compressed size



Ultralight Backpacking


Warm Weather


Regular: 12oz | 340g

Long: 13.6oz | 385g


Regular: 1.5 liters

Long: 2.2 liters

The Spark Ultralight Mummy Sleeping Bag Series spans everything from an ultralight down-filled liner, to a mid-winter fast-and-light sleeping bag. Each model uses premium materials and no-frills design to provide cutting-edge performance.Ultralight does not mean ultra-tight: The Spark mummy sleeping bags are snug but still have adequate wiggle room for the performance-oriented, backcountry user.

  • ULTRA-DRY Down 850+ Loft 90% Down Cluster Premium Goose Down certified Responsible Down Standard (RDS)
  • 10D shell and 7D liner materials help to achieve the incredible lightweight and compact packed size
  • Includes lightweight Ultra-Sil compression bag and storage cell
  • Zipper-length trimmed for gram-saving performance:
    • 50°F, 40°F, and 28°F have 1/3-length zippers
    • 18°F and 5°F have full-length side zippers
  • Baffle construction:
    • 50°F and 40°F have sewn-through construction
    • 28°F has baffles in the torso and sewn through in the leg area
    • 18°F and 5°F are fully baffled
  • Shape:
    • 50°F , 40°F and 28°F - Contoured mummy
    • 18°F and 5°F - Broader mummy

Tech Specs

  • BEST USE Ultralight Backpacking
  • COMES WITH Ultra-Sil™ compression bag and storage cell
  • INSULATION Ultra-Dry Down 850+ Loft
  • SHAPE Mummy
  • SHELL FABRIC Ultralight 10D Nylon Shell
  • ZIP OPTIONS Left-side #3 YKK zipper


40º Regular  40º Long
Spark 1 Spark 1
BAG WEIGHT 12oz 13.6oz
FILL WEIGHT 6.3 oz 7.2 oz
FITS UP TO HEIGHT 6 ft 6ft 4 in
SEASON RATING Warm Weather Warm Weather


Suitable for cooler temperatures?

Yes. The 5°F or possibly the 18°F will work in late Fall. The Spark 5°F will take you down to winter temperatures when paired with a greater than 3.5 R-Value sleeping mat like the Comfort Light Insulated.

Really suitable as a sleeping bag liner?

Yes. You could use the Spark 50°F, or even the Spark 40°F to boost the performance of a bag for cold-weather use. Adding one of these to a 20°F bag might make more sense than buying a 0°F bag for occasional winter use.

Able to be zipped to another sleeping bag?

No. Even though the 18°F or 5°F have full-length side zippers, they are not designed to be coupled to a sleeping bag with a right zipper (for instance the Flame 18°F or 5°F).