The Hyperlite Mountain Gear 20 Degree Sleeping Bag is a premium down sleeping bag insulated with 1000 fill power goose down and made with ultralight fabrics to keep its weight as low as possible. It has continuous baffles so you can shift the insulation to where you need it most, a highly breathable and ultralight 7D nylon shell, a 360-degree draft collar, a half-length zipper, and a parka-style hood. Priced at $650, it's a very competitive sleeping bag if minimizing your backpacking gear weight is your goal.

• Size Tested:  Regular
• Insulation: 1000 fill power grey goose down, treated
• Weight: 26.52 oz | 703 g (Actual weight on our scale –  28 oz | 792 g)
• Fill Weight: 16.5 oz | 454 g
• Zipper: Left Side, 1/2 length, dual sliders
• Draft Collar: 360-degree
• Draft Tubes: Yes
• Construction: Continuous baffles
• Shell fabric: 7D

• Shoulder Width 58.75 in | 149 cm

• Hip Width 57 in | 145 cm

• Footbox Circumference 40.0 in | 101.6 cm

• Length: 72 in
• Temperature has not been independently tested using the EN sleeping bag temperature rating standard
• Visit Hyperlite Mountain Gear for full specs

When temperatures fall below freezing, a mummy-style sleeping bag can be preferable to sleeping with a down quilt because it eliminates side drafts that can chill you. While there are alternative sleep insulation systems built around ultralight backpacking quilts, such as those from ZenBivy, which are also quite lightweight, nothing beats the simplicity of crawling into a mummy sleeping bag and chasing the chill away.

The Hyperlite Mountain Gear 20-degree sleeping bag is a premium bag designed to be as lightweight and compressible as possible, while still providing serious warmth and comfort. It is insulated with 1000-fill-power grey goose down (with a DWR finish for moisture resistance), which is the warmest and most compressible down insulation available. While impressive, that's just a little better than the 900-950 fill-power down sleeping bags out there already, and perhaps more flash than actual substance. But it certainly does catch your eye, doesn't it? The real value of Hyperlite's 20-degree sleeping bag lies in its construction and the careful selection of features and dimensions that make up the whole.

The Hyperlite 20 has a 360 degree draft collar and down filled draft tubes along its zipper to prevent drafts

Key Features

The Hyperlite 20 Sleeping bag has a beefy 360 draft collar with an internal adjustment cord to prevent warm air heated by your torso from escaping around your neck and shoulders when you move around at night, the so-called bellows effect. The bag has a natural-fitting parka-style hood with a cinch cord that is easy to reach when lying inside. A half-length zipper reduces weight and has two zipper sliders so you can open the lower one to vent the bag on warm nights. It is bordered by heavier fabric to prevent snags as well as a draft tube to prevent drafts from entering and chilling you. There's also a small pocket inside the bag to stash a smartphone or battery pack, but I'd recommend not uploading Instagram pictures of yourself if you insist on sleeping naked inside.

The interior of the sleeping bag is very roomy at the shoulders, hips, and foot box. I was impressed by that, although if you're 5'6″ or shorter, you should get the 66″ long sleeping bag so your body has to generate less warmth to heat up the bag. Women should consider the Hyperlite 20 a 30-degree sleeping bag because, on average, women have less body mass than men.

It's worth noting that the Hyperlite 20 sleeping bag has not been independently tested using the ISO sleeping bag standard, which uses a standard testing methodology for determining the temperature of a sleeping bag for men and women. That's not necessarily a showstopper because there are other premium bags on the market, such as those from Feathered Friends, which are still not tested, but Feathered Friends has been in the sleeping bag business for a long time and has a reputation for conservative and accurate temperature ratings.

The 900-fill power Therm-a-rest Parsec 20 (top) comes with a compression sack and packs smaller than the Hyperlite 20 in a 12L side entry pod

While it pairs well with the 12L Dyneema Side-Entry Pod that Hyperlite sent me with this bag, it's disappointing that Hyperlite doesn't include a Dyneema compression sack with the sleeping bag, when this would be such an obvious and useful enhancement. Check out UltralightSack's Dyneema Compression Sacks instead. If you're using an ultralight backpack from Hyperlite Mountain Gear or anyone else, being able to minimize pack volume is essential if you want to use a lower-volume, lighterweight backpack.

The sleeping bag has a parka-style hood with an easy-to-reach cinch cord for adjustment

Continuous Baffles

The Hyperlite 20-degree sleeping bag has continuous baffles to hold and position its down insulation. These can be a blessing or a curse to the uninitiated. Continuous baffles are fabric tubes that wrap around a sleeping bag to hold the insulation in place or let you move it to a different location by shaking the bag. They differ from box baffles, which hold the insulation in one spot.

For example, in hot weather you could move the insulation in the Hyperlite-20 to the bottom of the sleeping bag under your back, so it provides less insulation, and so you overheat less at night. In colder weather, you can do the opposite: position the down over the top of your chest and legs for more warmth, since heat rises. 

One problem with continuous baffles is that people don't understand that the down in their bags can move, even if you didn't consciously try to relocate it. As a result, they can think that their sleeping bag is defective. You also can't visually confirm where the down is since shell fabrics are not transparent, so you can't determine if your efforts to relocate the down insulation were successful. I think the Hyperlite 20 sleeping bag could have been just as competitive a product without its continuous baffles, and that they're unnecessary. I've owned other sleeping bags with continuous baffles and found their performance difficult to predict.

Comparable ultralight 15 and 20 down degree sleeping bags

Recomendation

The Hyperlite Mountain Gear 20 Degree Mummy Sleeping Bag is an ultralight, premium down sleeping bag designed for backpackers who want to minimize weight without sacrificing warmth. It uses 1000 fill power treated grey goose down, offering excellent warmth and compressibility, and weighs about 26.5 ounces (703 grams). The shell and lining are made from delicate but breathable 7-denier micro-ripstop nylon, which requires careful handling. The bag features a 360-degree draft collar, a half-length zipper with draft tubes, and a parka-style hood with an adjustable cinch cord to keep warmth in and drafts out. Its roomy interior adds comfort, while the continuous baffle construction lets you shift insulation where it’s needed most, though this design can be tricky since the down may move unintentionally and isn't visible through the fabric.

One important consideration is that the bag has not been independently tested to recognized temperature standards, so the stated 20-degree rating is based on estimates rather than verified data; smaller users and women may find it closer to a 30-degree bag. The lack of an included compression sack and the delicate fabric also mean extra care and expense for packing and maintenance. While the price is high at $650, the Hyperlite Mountain Gear 20 Degree Sleeping Bag is a strong choice for experienced ultralight backpackers who prioritize weight savings, high-quality down, and advanced draft protection. However, those seeking more durability, verified warmth ratings, or simpler construction might want to consider alternatives.

Disclosure:  While Hyperlite Mountain Gear sent us a sample bag to review, they did not “sponsor ” or pay us to write a gear review. The views contained here are entirely our own.

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