Zpacks
Zpacks Classic Sleeping Bag 20F
No citable owner-review average published for this one, so no stars.
A sleeping bag with no zipper at all: a sewn tube with a hood, which is the lightest way to build a closed bag and the reason 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. Getting in and out means going through the top, and the bag cannot be vented on a warm night.
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
- Hydrophobic down
- RDS down
- Wide option
- Made in USA
What it does well
- 18.8 ounces for a hooded 20-degree bag is quilt weight with none of a quilt's draft 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.
- 900-fill water-repellent down, made in Florida, with a shell weight listed separately from the down weight.
- Sewn-through construction means nothing to snag, nothing to jam and nothing to fail.
What it costs you
- No zipper at all — you cannot vent it, you cannot use it as a blanket, and you get in through the top.
- No ISO or EN rating; the 20 °F number is Zpacks's own, and the loft figure is the only checkable thing behind it.
- 10-denier 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
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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 the one entry here where the marketing number and the lab number sit only nine degrees apart — it is called a 20 and it tests to a 29 °F comfort figure and an 18 °F limit, which is about as close to truth-in-labelling as the 20-degree class gets. 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 sheetREI Co-op
REI Co-op Magma 15
The Magma is the bag most people who compare specs end up buying, and the numbers explain why: 850-fill down, 23.3 ounces of it, an ISO comfort rating of 21 °F and an ISO lower limit of 9 °F, for $399. That is a genuinely six-degrees-warmer comfort figure than the 15 in the name, which is the opposite direction from almost every other bag in this catalogue — REI named the bag closer to its limit than its comfort and then published both, which is the honest way round.
Best for: Backpackers who want the best published numbers per dollar
Full spec sheet