The Sea to Summit Alpine -20F is a down bag rated to a standardized comfort of -2°F, weighing 3 lb 3.0 oz. It uses 850-fill-power down, and packs to 14.0 L, starts at $984.
GearScore breakdown
How this bag earns its 77 on the default algorithm, factor by factor
Have specific needs in mind — winter warmth, ultralight backpacking, or a bag on a budget? Rank this bag against every other on your own custom scoring algorithm.
Open the full bag comparison →Specifications
Temperature & provenance
The maker publishes a single self-assigned rating (no EN/ISO lab test). Maker ratings follow the survival-oriented "limit" convention and run optimistic, so for scoring we standardize it to a comfort-equivalent of -2°F (a documented, uniform adjustment). This is how a lab-verified bag out-ranks an optimistic marketing number.
| Style: | Bag |
|---|---|
| Shape: | Mummy |
| Fill: | Down |
| Insulation: | 850+FP Ultra-Dry goose down |
| Fill power: | 850 FP |
| Fill weight: | n/s |
| Weight: | 3 lb 3.0 oz1.45 kg |
| Packed volume: | 14.0 L |
| Warmth-to-weight: | 5.0 /100g |
| Price per warmth: | $14 /warm |
How scoring works
The same GearScore engine the comparison pages use. This is the default weighting; open the full comparison to re-weight it around your trip.
GearScore blends published specs into one 0 to 100 number. Warmth (a standardized comfort rating) is a "good enough" gate; weight and packed size score on a sliding scale. Price and fill power are levers presets turn on.
Customize on the full comparison →- Sufficiency
- Only needs to be good enough. Warmth works this way: clear your target temperature and you're set, extra warmth adds no points.
- Monotonic
- More (or less) is always better. Lighter beats heavier and smaller packs beat bigger, so they score on a sliding scale.
- Preference
- Style, fill, and shape are personal preference, never scored. They only filter the list.