The Spark Ultralight 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 for the designed end-use.

Ultralight does not mean ultra-tight: The Spark sleeping bags are snug but still have adequate girth for the performance-oriented backcountry user.

Is this down sleeping bag...

Suitable for cooler temperatures? Yes. You would want the Spark 5° F or possibly the 18° F - either bag will work in late Fall, the 5° F will take you down to winter temperatures when paired with an adequately insulating 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 or 28° F to boost the performance of a bag for cold-weather use. Adding one of these to a 20° F / -5° C bag might make more sense than buying a "0° F / -20° C" bag for only 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).

Features

• Best Use: Ultralight Backpacking, Bike Touring, Liner Bag
• Performance: 2 Season: 28° F (comfort range 28° F to 60° F)
• ULTRA-DRY Down 850+ Loft 90% Down Cluster Premium Duck 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: 28° F bag has 1/3-length zippers
• Baffle construction: 28° F bag has baffles in the torso and sewn through in the leg area.

Specs:

• Comes With: Ultra-Sil compression bag and storage cell
• Insulation: Ultra-Dry Down 850+ Loft
• Shell Fabric: Ultralight 10D Nylon Shell
• Zip Options: Left-side #3 YKK zipper
• Bag Series : Sp 0
• Fits Up To: 6 ft / 183 cm (Reg), 6 ft 4 in / 192 cm (Long)
• Season Rating: Summer or Sleeping Bag Liner
• Temperature (EN RATING): Comfort range 50°F to 70°F
• Women's Temp (EN RATING): 54° F (Comfort)