Therm-a-Rest
Therm-a-Rest Parsec 20
No citable owner-review average published for this one, so no stars.
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.
Label against lab
Sold as a 20 °F bag; its EN 13537 comfort rating is 29 °F, which is 9 °F warmer than the name suggests. Plan around the comfort figure, not the label. Why the gap exists
At that temperature the pairing table wants at least an R 4 pad underneath it.
Size run
One product, 2 sizes. The headline numbers on this page describe the Regular.
| Size | Weight | Approx. price | Length | Shoulder girth |
|---|---|---|---|---|
| Regular | 1 lb 13 oz | ~$470 | 80 in | 62 in |
| Long | 1 lb 15 oz | ~$500 | 85 in | 65 in |
Specifications
Highlights
Features
- ISO or EN rated
- Hydrophobic down
- RDS down
- Draft collar
- Full-length zipper
- Recycled fabric
- Stash pocket
What it does well
- 900-fill down is the highest fill power of any mainstream-brand bag here, and it is what gets a hooded 20-degree mummy to 29 ounces.
- Published EN comfort (29 °F) and limit (18 °F) figures, so the rating can be checked rather than trusted.
- 62-inch shoulder girth is roomy for an ultralight bag — most of its weight class runs 57 to 60.
- Zoned fill puts the down where it lofts and skips the crushed panel under your back.
- Duck down is RDS-certified and treated with a PFAS-free hydrophobic finish.
What it costs you
- $470 is cottage-brand money for a bag made in Vietnam rather than a cottage workshop.
- 20-denier shell is not the most durable in the class; a 900-fill bag deserves care around campfires and rough granite.
- Only two lengths and no wide option, so a broad sleeper has nowhere to go.
- 900-fill down is the first thing to suffer from damp storage or a hot dryer, and this bag has a lot of value tied up in it.
Those two lists are drawn from Therm-a-Rest’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
Distilled from owner discussions and long-term published reviews, not from anything measured here.
The Parsec occupies a quiet middle ground in owner discussion: recommended, rarely enthused about. It appears most often in lists of good options alongside the mid-market bags people actually argue about, which is a respectable place to be and not a memorable one.
What little detail exists is practical rather than evaluative. Owners at the upper end of a size's height range ask whether to size up and do not get confident answers, which is a real gap when the maker publishes fits-up-to heights rather than internal lengths.
For a bag with published lab figures at this weight, the low discussion volume is the most surprising thing about it.
What owners like
- It turns up as the solid, slightly cheaper alternative when someone is looking at premium European down bags and balking at the price.
- Owners group it with the best-regarded mid-market bags rather than with the budget tier, which is where its price sits.
- The published lab figures mean people recommending it can point at a number rather than at a reputation.
- Owners who use the colder versions in the same line keep them in rotation alongside quilts, which suggests the fit works.
Common complaints
- Discussion volume is low, so there is little accumulated detail on how it holds up.
- Sizing questions come up without confident answers — owners at the top of a size's height range are unsure whether to size up.
- It is usually mentioned as an alternative rather than as a first choice, which says something about its profile.
Questions owners ask
Should I size up if I am at the top of the height range?
How does it compare with the premium down bags?
Is there much long-term owner data?
Therm-a-Rest Parsec 20, head to head
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