Sea to Summit Spark 30°F review

The Spark is for hikers who care more about weight than warmth. The 30°F Regular weighs 17.4 oz (493 g) with 9.3 oz of 850+ fill power goose down, and compresses to 4.5 L, the lightest and smallest bag on this list. Sea to Summit tests to ISO 23537 and lists a 30°F lower limit and a 39°F women's comfort rating, so it is a summer and early fall bag, not a shoulder season one. The down is RDS-certified with a non-PFAS Ultra-Dry Down treatment, and the 10D shell has a non-PFAS DWR with more water-resistant fabric at the hood and footbox. The 30°F version uses hybrid box baffles in the torso and sewn-through baffles in the legs. Sea to Summit also sells 45°F, 15°F and 0°F versions, from $349 for the 45°F. At $449, it costs less than the Swallow UL 20 but is rated 10°F warmer, which is why it sits lower on value.

Who it is for

summer and early fall backpackers counting every ounce

Price

$449 for the 30°F Regular at the Sea to Summit US store when checked; the 45°F version is $349.

Spark Down Sleeping Bag $449.00
Quoted from the vendor pricing page on November 12, 2026.

Key features

• 850+ fill power goose down with Ultra-Dry Down treatment
• 17.4 oz (493 g) for the 30°F Regular
• ISO lower limit 30°F; women's ISO comfort 39°F
• 10D nylon shell and liner
• 4.5 L compressed volume

Strengths and weaknesses

• Strength: The lightest bag on this list at 17.4 oz
• Strength: Packs to 4.5 L, the smallest here
• Strength: Full-length zip versions zip to a women's Spark for couples
• Weakness: 30°F ISO lower limit is too warm for frosty nights
• Weakness: $449 is a lot for a three-season bag rated at 30°F
• Weakness: 10D fabrics need more care than 20D shells

Key facts

• Price: $449 (30°F Regular)
• ISO lower limit / comfort: 30°F / 39°F
• Weight: 17.4 oz (493 g)
• Insulation: 850+ fill goose down
• Fits up to: 6 ft 1 in

Where it ranks

Sea to Summit Spark 30°F is No. 8 in our Best Sleeping Bags verdict.