Sea to Summit Spark Ultralight 40F Sleeping Bag

Features

• Superlight 7-denier and 10-denier fabrics offer minimal weight and packed size
• 850+ fill-power Premium Goose UltraDry Down™ certified to the Responsible Down Standard (RDS) and provides maximum insulation value
• Contoured mummy shape provides comfort and efficient insulation
• Vertical chest baffles prevent down migration
• Note: This bag is not designed to zip with another

Imported.

Many sleeping bags are rated for temperature by an independent testing protocol. REI and the broader industry now use the International Organization for Standardization (ISO) 23537 protocol, which improves on the older European Norm (EN) 13537 standard; you may still see older items in our assortment that were only EN tested. With either protocol, each bag gets a Comfort (or T-Comfort) rating and Lower Limit (or T-Limit) rating. The Comfort rating is the lowest temperature at which the bag will keep the average “cold sleeper” comfortable, and the Lower Limit rating is the lowest temperature at which the bag will keep the average “warm sleeper” comfortable. Ratings are based on a person wearing one long underwear layer and a pair of socks, sleeping on an insulated surface with a minimum R-value of 5.38. Many brands use the Comfort rating for women’s bags and the Lower Limit rating for men’s and unisex bags. Everyone’s body and sleep comfort differ, and conditions of use (posture, clothing, sleeping pad R-value, wind, humidity, etc.) affect total insulation, so EN and ISO ratings are intended as a guideline to help you compare products, rather than a guarantee of warmth.View all Sea to Summit Backpacking Sleeping Bags

Technical Specs

Best Use

Tested Lower Limit

Tested Comfort

Temperature Rating (F)

Temperature Rating (C)

Weight

Ultralight

Shell

Zipper Location

Insulation Type

Water-Resistant Down

Fill

Fill Weight

Lining

Sleeping Bag Shape

Fits Up To (in.)

Shoulder Girth (in.)

Hip Girth (in.)

Stuff Sack Size

Stuff Sack Volume

Compressed Volume

Gender

Sustainability

Backpacking

40 degrees (F) – EN

48 degrees (F) – EN

40 degrees (F)

5 degrees (C)

Regular: 12 ounces Long: 13.6 ounces

Yes

10-denier nylon

Left

Down

Yes

850+ UltraDry Down

Regular: 6 ounces Long: 7 ounces

7-denier nylon

Mummy

Regular: 72 inches Long: 76 inches

Regular: 59 inches Long: 62 inches

Regular: 51 inches Long: 54 inches

Unavailable

Unavailable

Unavailable

Unisex

Down certified to the Responsible Down Standard (RDS)