Marmot Trestles Elite Eco 20 vs Kelty Cosmic Down 20
In short: The Marmot Trestles Elite Eco 20 costs $1 less; the Marmot Trestles Elite Eco 20 is rated 7 °F colder on the figure each maker publishes; the Kelty Cosmic Down 20 saves 17.4 oz; one is down and the other synthetic, which decides it if your trips are wet.
| Spec | Marmot Trestles Elite Eco 20 | Kelty Cosmic Down 20 |
|---|---|---|
| Approx. price | ~$189 | ~$190 |
| ISO comfort | 24 °F | 31 °F |
| ISO limit | 12 °F | 21 °F |
| Rating on the label | 20 °F | 20 °F |
| Honesty gap | 4 °F | 11 °F |
| Rating standard | ISO 23537 | ISO 23537 |
| Weight | 3 lb 8.4 oz | 2 lb 7 oz |
| Warmth per ounce | 0.64 °F/oz | 0.74 °F/oz |
| Fill | Synthetic | 550 fill power down |
| Fill weight | 43.6 oz | 16.4 oz |
| Loft budget | — | 9.0k in³ |
| Shape | mummy | semi-rectangular |
| Shoulder girth | 60 in | 62 in |
| Zipper | full | full |
| Shell fabric | 100% recycled polyester | Recycled 20D nylon taffeta, PFAS-free DWR |
| Hydrophobic down | — | No |
| Packed size | not published | not published |
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
Marmot Trestles Elite Eco 20
- ISO comfort of 24 °F for $189 — the cheapest genuinely warm lab-rated bag in this catalogue.
- 100% recycled shell and HL-ElixR Eco fill, which is unusual at this price.
- Synthetic insulation keeps working wet, and doesn't need the careful storage down does.
- A second short zip at the foot lets you vent without opening the whole bag.
- 56.4 ounces — three and a half pounds, and it packs big.
- Synthetic fill loses loft with repeated compression faster than down does.
- Shoulder girth is 60 inches in the Regular, which is average; the Long X-Wide is the only roomy cut.
- Four sizes, but the Long X-Wide is the only wide one and it weighs over four and a half pounds.
Kelty Cosmic Down 20
- Publishes both ISO figures — comfort 31 °F, limit 21 °F — at a price where most competitors publish neither.
- Semi-rectangular cut with a wide footbox; far less confining than a true mummy.
- Full draft tube and collar, a zippered internal stash pocket and a stuff sack in the box, at a price where some of those get skipped.
- $190 for a real down bag, and Kelty's trapezoidal baffles keep the fill from migrating.
- 550-fill down means the loft comes from volume: 39 ounces and a large packed size.
- The 31 °F comfort figure is eleven degrees off the 20 in the name.
- The 550-fill down is untreated and carries no RDS certification on Kelty's spec sheet, which the price explains.