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Mummy vs rectangular vs spoon bags and quilts

Mummy, rectangular and spoon shapes trade thermal efficiency against movement room.

How to use this answer

Match shoulder and hip dimensions to your sleeping posture. This separates a useful measurement from a broad product label and helps identify which exact variant needs further checking.

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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.

How a quilt differs

A backpacking quilt leaves much of the underside open and relies on pad attachment and draft control. This differs from each enclosed bag shape. Compare width, attachment straps and a documented rating method; a quilt temperature label should not be treated as an ISO adult-bag comfort result without a verified test.

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 variantProduct labelComfortListed weight
EXPED Terra 15 — Small / Left Zip15°F (-9.4°C)25°F (-3.9°C)2.66 lb (1,205 g)
Marmot Trestles 30 — Regular / Right Zip30°F (-1.1°C)36°F (2.3°C)3.04 lb (1,380 g)
Big Agnes Sidewinder 20 — Small20°F (-6.7°C)30°F (-1.1°C)2.25 lb (1,020 g)

These records illustrate how the reported measurements and source links are presented; they are not personal field tests or ranked recommendations.

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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.