Fill power describes down loft per unit mass; fill weight is the actual amount used.
How to use this answer
Compare both numbers and bag construction, not fill power alone. This separates a useful measurement from a broad product label and helps identify which exact variant needs further checking.
Decision boundary
The listed values describe a product under its stated source conditions. They do not establish personal comfort, safety, stock, or fit in every shelter.
Temperature and fit context
ISO 23537-1:2022 describes adult bag testing under controlled conditions. Product labels and untested claims are not interchangeable with comfort or lower-limit numbers. A sleeping pad, clothing, humidity and individual metabolism change real comfort.
For this question, check: ISO comfort and lower limit where available, maximum user height, shoulder room, fill and actual pad insulation. When a particular specification is absent, keep the decision open rather than treating a missing value as zero or assuming a universal fit.
Compare actual recorded values
The values below come from exact catalog variants. The table is an illustration of which measurements to compare, not a ranking or a recommendation. Open each card for the field source and revision notes.
| Exact variant | Product label | Comfort | Listed weight |
|---|---|---|---|
| Rab Mythic 20 — Long | 20°F (-6.7°C) | 32°F (0.0°C) | Not verified |
| Mountain Hardwear Phantom 0F/-18C — Short | -0°F (-17.8°C) | 12°F (-11.1°C) | Not verified |
| Therm-a-Rest Parsec 20F/-6C — Regular / 900FP | 20°F (-6.7°C) | 29°F (-1.7°C) | 1.81 lb (820 g) |
These records illustrate how the reported measurements and source links are presented; they are not personal field tests or ranked recommendations.
Before you rely on a number
Recheck manufacturer instructions and the exact year, size and SKU. The October 30, 2026 dataset does not verify real-time inventory, sale prices, field performance or a guaranteed safe temperature. If the key measurement for this question is unavailable, ask the maker or measure your own equipment before committing to a setup.
Sources and further reading
Source pages and product listings can change. Specifications were assembled from the supplied dataset as of October 30, 2026; current availability is not guaranteed.
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