REI Co-op Magma 15 vs Zpacks Classic Sleeping Bag 20F

Weight and specs compared for 2026 — and which one to choose.

Zpacks Classic Sleeping Bag 20F is the lighter option — 503 g lighter than the REI Co-op Magma 15 (59% less weight). If grams matter to you, that is the one to beat.

Spec	REI Co-op Magma 15	Zpacks Classic Sleeping Bag 20F
Weight	850 g · 0.850 kg · 1.87 lb	347 g · 0.347 kg · 0.77 lb
Brand	REI Co-op	Zpacks
Category	Sleep System	Sleep System

REI Co-op Magma 15

850 g

850-fill down sleeping bag rated to 15°F. Great value.

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Zpacks Classic Sleeping Bag 20F

347 g

Mummy-style sleeping bag rated to 20F (-7C) with 900-fill goose down. DCF outer shell for low weight and packability. Water-resistant treatment included.

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REI Co-op Magma 15 vs Zpacks Classic Sleeping Bag 20F: which should you buy?

If saving weight is your priority, the Zpacks Classic Sleeping Bag 20F wins — at 347 g it is 503 g (59%) lighter than the REI Co-op Magma 15 (850 g). That said, the heavier option may justify the extra grams with more capacity, durability or comfort, so weigh the trade-off against how you'll use it.

See where both rank against everything else in this category on the lightest sleep system page, or browse the full gear weight database.

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