Head-to-head · Best 0 Degree Sleeping Bags

Mountain Hardwear Phantom 0F/-18C vs Sea to Summit Spark 0F

Which is the better buy? Side-by-side on rating, price, strengths, and watch-outs — with the published ratings we averaged to get there.

The short answer

Sea to Summit Spark 0F comes out ahead by a narrow margin (4.2 vs 4.4). The gap is mostly about Gram-counting ultralight backpackers who want the smallest, lightest true 0°F down bag and camp in dry cold. — read the strengths below before deciding.

Ranked #5 in Best 0 Degree Sleeping Bags

Mountain Hardwear Phantom 0F/-18C

4.2

$700as of Jun 7

The Phantom 0 is a polarizing bag: CleverHiker calls it 'one of the warmest backpacking sleeping bags we've tested' while OutdoorGearLab found it 'freezing all night' at zero degrees. It pairs a light 800-fill build with a buttery-soft 20D shell and a narrow, weight-efficient cut. Real owners on Trailspace report comfort to 2°F, so fit and individual metabolism clearly matter with this one.

Strengths

— Excellent warmth-to-weight ratio in a roughly 2 lb 11 oz package
— Smooth, soft 20D nylon taffeta shell that's pleasant against skin
— Massive draft tubes and effective hood cinches to seal in heat

Watch-outs

— OutdoorGearLab tested it 'freezing all night' at 0°F and scored it 56/100
— Thin shell fabric can let feathers shift and create cold spots
— Narrow cut feels restrictive for stomach and starfish sleepers

$700 · Buy at mountainhardwear.com Full review →

Higher ratedRanked #4 in Best 0 Degree Sleeping Bags

Sea to Summit Spark 0F

4.4

$349as of Jun 8

The Spark 0F is the ultralight of this group, packing a genuine 0°F-rated bag into about 2 lb 7 oz and a sub-10-liter stuff size. It uses 850+ fill Ultra-Dry down and reviewers find its temperature rating accurate. The trade-offs are a snug, less-forgiving cut and a thin shell that offers little wet-weather protection, plus a steep price for the warmth.

Strengths

— Among the lightest 0°F down bags at roughly 2 lb 7 oz
— Sub-10-liter packed size, the most compressible bag here
— 850+ fill power Ultra-Dry treated goose down resists moisture

Watch-outs

— Snug ultralight cut is less forgiving than the Kodiak or Ibis
— Thin shell offers little wet-weather protection
— Pricey at roughly $649-$679 for the warmth delivered

$349 · Buy at seatosummit.com Full review →

How they stack up

Mountain Hardwear Phantom 0F/-18C

The most divisive bag here, lighter than the Western Mountaineering Kodiak MF and Feathered Friends Ibis ES 0 but with sharply split warmth verdicts, and less of a sure thing than the Therm-a-Rest Parsec 0F or the ultralight Sea to Summit Spark 0F.

Sea to Summit Spark 0F

The lightest and most compressible bag here, undercutting the Therm-a-Rest Parsec 0F on weight and packed size and far lighter than the Western Mountaineering Kodiak MF, Feathered Friends Ibis ES 0 and Mountain Hardwear Phantom 0, but with a snugger cut and a thin, less weatherproof shell.

Specs side-by-side

Spec	Mountain Hardwear Phantom 0F/-18C	Sea to Summit Spark 0F
Temperature Rating	0°F limit / 13°F comfort	0°F limit / 14°F comfort
Fill Power	800-850 goose down	850+ Ultra-Dry goose down
Fill Weight	2.04 lb	29.6 oz (840 g)
Total Weight	2 lb 11 oz - 3 lb (long)	2 lb 7 oz (1113 g)
Shell	20D nylon taffeta	Ultralight nylon
Cut	Narrow mummy	Snug ultralight mummy
Features	Draft tubes, hood cinches	—
Warranty	Limited lifetime	—
Packed Size	—	9.9 L
Zipper	—	Full-length YKK with draft tube

← See the full ranking of best 0 degree sleeping bags