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Head-to-head · Best Backpacking Sleeping Bags

Kelty Cosmic Down 20 vs Mountain Hardwear Phantom 30

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

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The short answer

Mountain Hardwear Phantom 30 comes out ahead by a clear margin (4.4 vs 4.0). Mountain Hardwear Phantom 30 is best for: ultralight backpackers seeking warmth. Read the strengths below before deciding.

Kelty Cosmic Down 20
Ranked #3 in Best Backpacking Sleeping Bags
Kelty Cosmic Down 20
2 sources$209.95as of Oct 29

The Kelty Cosmic Down 20 puts real down in a budget bag, cut in a tapered mummy shape. Its 550-fill down isn't as thermally efficient as pricier insulation, so reviewers steer it toward summer camping and mild nights. The thicker shell fabric makes it tougher than ultralight bags, at the cost of weight and bulk. Casual backpackers who want down without the premium price will do fine; anyone expecting sub-freezing temperatures should look elsewhere.

Strengths
  • — More packable than most budget options with synthetic fill
  • — Relatively thick polyester fabric is more resilient than thin ultralight material
  • — Includes full-length draft tube and insulated collar for heat retention
Watch-outs
  • — Cut-rate 550-fill down places it at the low end for warmth-to-weight
  • — Runs colder than its temp rating
$209.95 · Check Price on AmazonFull review →
Mountain Hardwear Phantom 30
Higher ratedRanked #1 in Best Backpacking Sleeping Bags
Mountain Hardwear Phantom 30
2 sources$579.99as of Oct 29

The Mountain Hardwear Phantom 30 earns its praise on warmth-to-weight: 850-fill down, 10 ounces of it, stacking up four inches of loft. Reviewers found it holds around freezing and a little below, packs down small, and comes with an adjustable hood and draft collar. Cold sleepers and anyone heading into extreme conditions should skip it. Ultralight backpackers balancing weight against warmth are the fit.

Strengths
  • — Excellent warmth-to-weight ratio due to 850-fill down
  • — Four inches of loft from 10 ounces of down fill
  • — Adjustable hood with even face gasket closure
Watch-outs
  • — Limited space for larger or wider users
  • — Not suitable for extreme cold conditions
$579.99 · Check Price on AmazonFull review →

How they stack up

Kelty Cosmic Down 20

At 2 lb 7 oz it weighs over a pound more than the 1 lb 6 oz Phantom 30, and it costs far less. It is a down bag where the REI Co-op Trailmade 25 uses synthetic insulation, and it is lighter than the Trailmade's 3 lbs 4.6 oz.

Mountain Hardwear Phantom 30

Unlike the REI Co-op Trailmade 25, which prioritizes value and sizing, the Mountain Hardwear Phantom 30 focuses on warmth-to-weight with its 850-fill down. At 1 lb 6 oz it weighs less than half the Trailmade's 3 lbs 4.6 oz, and it is over a pound lighter than the 2 lb 7 oz Kelty Cosmic Down 20, which uses 550-fill down. It costs far more than the Kelty.

Specs side-by-side

SpecKelty Cosmic Down 20Mountain Hardwear Phantom 30
Temperature Rating31/21°F (ISO Comfort/Limit)30°F/-1°C
Fill Power1 lb. 0.4 oz. of 550-fill down850
Weight2 lb. 7 oz.1 lb 6 oz/624 g
Insulation550-fill-power down—
Shell Fabric20D nylon—
Packed Volume10.7L—
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