Zpacks
Zpacks Classic Sleeping Bag 20F
No citable owner-review average published for this one, so no stars.
A hoodless sleeping bag with a three-quarter-length zipper run along the bottom instead of the side: closed around the back like a bag, vented like a quilt when the zip is open, and no draft tube because the zipper sits under you — which is how the Standard/Medium comes in at 18.8 ounces for a 20-degree rating. Zpacks publishes target loft (2.5 inches for the 20 °F version) and exact shell and down weights for every one of the twenty-one size combinations, which is more transparency about construction than anyone else in this catalogue offers — and no lab rating at all, which is less transparency about temperature. There is no hood: an elastic cord cinches around the neck, and Zpacks's answer for cold nights is a warm hat or its separate down hood.
Label against lab
No ISO or EN rating is published for this one — the 20 °F is Zpacks’s own figure, with no lab test behind it. Where a maker publishes loft or fill weight instead, those are the numbers worth comparing. What the standards measure
At that temperature the pairing table wants at least an R 4 pad underneath it.
Size run
One product, 7 sizes. The headline numbers on this page describe the Standard / Medium.
| Size | Weight | Approx. price | Length | Shoulder girth |
|---|---|---|---|---|
| Slim / Short | 1 lb 0.5 oz | ~$449 | 68 in | 55 in |
| Slim / Medium | 1 lb 1.3 oz | ~$469 | 74 in | 55 in |
| Standard / Short | 1 lb 1.7 oz | ~$469 | 68 in | 60 in |
| Standard / Medium | 1 lb 2.8 oz | ~$489 | 74 in | 60 in |
| Standard / Long | 1 lb 3.8 oz | ~$509 | 80 in | 60 in |
| Broad / Medium | 1 lb 4 oz | ~$509 | 74 in | 65 in |
| Broad / Long | 1 lb 5 oz | ~$529 | 80 in | 65 in |
Specifications
Highlights
Features
- RDS down
- Wide option
- Made in USA
What it does well
- 18.8 ounces for a closed 20-degree bag is quilt weight with none of a quilt's draft-around-the-back problem.
- Twenty-one size combinations across three girths and three lengths, each with its own published weight.
- Publishes target loft in inches, which is a more useful comparison between down bags than a temperature number is.
- 950-fill untreated Muscovy duck down, made in Florida, with a shell weight listed separately from the down weight.
- The bottom-run zipper opens the bag flat for venting and needs no draft tube, so there is nothing to snag on the way in.
What it costs you
- No hood: below freezing you are wearing a hat or buying Zpacks's down hood separately.
- No ISO or EN rating; the 20 °F number is Zpacks's own, and the loft figure is the only checkable thing behind it.
- The 0.51 oz/sq yd Ventum shell is fragile enough that a tent-floor rock is a real risk.
- $489 for the middle size, and custom options push it higher.
Those two lists are drawn from Zpacks’s published specifications and from reviews that measured them. They are not owner sentiment — anything owners said appears under its own heading below.
What owners say
No owner discussion has been collected for the Zpacks Classic Sleeping Bag 20F yet. The pros and cons above come from Zpacks’s published specifications and from reviews that measured them — nothing on this page claims owners said anything. How that works.
Zpacks Classic Sleeping Bag 20F, head to head
Others in the same band
More from Zpacks →
Feathered Friends
Feathered Friends Swallow YF 20
Feathered Friends sew every bag in Seattle and publish girth at four points — shoulder, elbow, hip and footbox — which tells you more about whether a bag will fit than any temperature rating can. The Swallow is their three-season workhorse: 900-fill-power Muscovy down, 16.8 ounces of it, in a 59-inch-shoulder mummy that weighs 29.2 ounces. Like Western Mountaineering they publish no ISO figure, and like Western Mountaineering they have a forty-year record that people buy on instead.
Best for: Three-season backpacking where fit matters as much as warmth
Full spec sheet
Therm-a-Rest
Therm-a-Rest Parsec 20
The Parsec is the lightest hooded mummy Therm-a-Rest makes, and one of the more honestly named bags here — it is called a 20 and it tests to a 29 °F comfort figure and an 18 °F limit, a nine-degree gap that only the Marmot Trestles Elite Eco beats among the 20-degree bags in this catalogue. Seventeen ounces of 900-fill duck down inside a 20-denier recycled shell gets the whole bag to 29 ounces. The zoned baffles put more down on top and less underneath, on the correct theory that the down you lie on is doing nothing, and the shoulder girth is a generous 62 inches for a bag this light.
Best for: Three-season backpackers who want a hooded bag near quilt weight
Full spec sheet
Big Agnes
Big Agnes Torchlight EXP 20
Two zippered expansion panels run from shoulder to footbox and add five inches of girth on each side — ten inches in total — which makes this the only bag here whose fit you can change after you have bought it. Zip them shut on a cold night and it is a normal mummy; open them on a warm one and it is closer to a semi-rectangular bag. That is a genuinely good answer to the problem that a bag tight enough to be warm is too tight to sleep in. The trade is 40 ounces and a manufacturer-only 20-degree rating with no lab figure behind it.
Best for: Sleepers who want a mummy some nights and room on others
Full spec sheet