Big Agnes Torchlight EXP 20 vs REI Co-op Magma 15
In short: The Big Agnes Torchlight EXP 20 costs $19 less; the Big Agnes Torchlight EXP 20 is rated 8 °F colder on the figure each maker publishes; the REI Co-op Magma 15 saves 11.8 oz; only the REI Co-op Magma 15 publishes a lab temperature rating at all.
| Spec | Big Agnes Torchlight EXP 20 | REI Co-op Magma 15 |
|---|---|---|
| Approx. price | ~$370 | ~$389 |
| ISO comfort | not published | 28 °F |
| ISO limit | not published | 16 °F |
| Rating on the label | 20 °F | 15 °F |
| Honesty gap | — | 13 °F |
| Rating standard | manufacturer | ISO 23537 |
| Weight | 2 lb 8 oz | 1 lb 12.2 oz |
| Warmth per ounce | — | 1.13 °F/oz |
| Fill | 650 fill power down | 850 fill power down |
| Fill weight | not published | 15.9 oz |
| Loft budget | — | 13.5k in³ |
| Shape | mummy | mummy |
| Shoulder girth | not published | 63 in |
| Zipper | full | half |
| Shell fabric | 20D recycled polyester ripstop, PFAS-free DWR | Pertex 15-denier ripstop nylon |
| Hydrophobic down | Yes | Yes |
| Packed size | not published | 5.2 L |
Shaded cells mark the row where one has a measurable advantage. Weight, thickness, girth and shape are left unshaded on purpose: heavier is sometimes tougher, wider is sometimes warmer, and calling a winner on those would be an opinion dressed as a measurement.
What each one does well, and costs you
Big Agnes Torchlight EXP 20
- Ten inches of expandable girth across two zippered side panels — the only adjustable-fit bag in this catalogue.
- The PadLok system attaches the bag to a pad so you roll inside it rather than rolling off.
- 650-fill DownTek is PFC-free hydrophobic and RDS-certified.
- 20-denier recycled polyester shell is tougher than the nylon used on most bags at this price.
- Three lengths, and the expansion panels mean each length covers a wider range of builds.
- No ISO or EN figure at all — the 20 is Big Agnes's own number and there is nothing published to check it against.
- 40 ounces in the Regular, heavy for a 20-degree down bag.
- The expansion panels add zips, weight and two more seams that can leak heat.
- Big Agnes publishes neither fill weight nor shoulder girth, so it can't be compared on the physical numbers.
- Opening the panels means heating a much larger volume, so the 20-degree claim only applies zipped shut.
REI Co-op Magma 15
- Publishes both ISO figures, and the 16 °F lower limit lands within a degree of the name — the comfort figure is the one to plan around.
- 28.2 ounces with 15.9 ounces of 850-fill goose down, in the same ISO 28/16 bracket as Sea to Summit's Spark 15 for $160 less.
- Pertex 15-denier shell and lining, water-resistant down, a 63-inch shoulder girth and a 5.2-litre compressed volume — REI publishes all of it.
- Sold through a co-op with a real returns policy, which matters for a bag whose fit you cannot judge in a photograph.
- The 28 °F comfort figure is thirteen degrees off the 15 in the name — tied for the widest gap in this catalogue — so a cold sleeper should treat it as a high-20s bag.
- Reviews written before the 2026 revision describe a heavier, warmer bag; check the date before trusting a figure.
- Two lengths and one width, in left or right zip; there is no built-to-order width or overfill option.