REI Co-op Magma 15 vs Western Mountaineering AlpinLite 20

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

REI Co-op Magma 15 is the lighter option — 29 g lighter than the Western Mountaineering AlpinLite 20 (3% less weight). If grams matter to you, that is the one to beat.

Spec	REI Co-op Magma 15	Western Mountaineering AlpinLite 20
Weight	850 g · 0.850 kg · 1.87 lb	879 g · 0.879 kg · 1.94 lb
Brand	REI Co-op	Western Mountaineering
Category	Sleep System	Sleep System

REI Co-op Magma 15

850 g

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

Full details →

Western Mountaineering AlpinLite 20

879 g

Roomy 20F mummy bag with 850+ goose down and continuous baffles, balancing warmth, comfort and low weight.

Check price Full details →

REI Co-op Magma 15 vs Western Mountaineering AlpinLite 20: which should you buy?

If saving weight is your priority, the REI Co-op Magma 15 wins — at 850 g it is 29 g (3%) lighter than the Western Mountaineering AlpinLite 20 (879 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.

More sleep system comparisons

REI Co-op Magma 15 vs Sea to Summit Aeros Ultralight Pillow (Regular) REI Co-op Magma 15 vs NEMO Equipment Tensor Elite Sleeping Pad REI Co-op Magma 15 vs Therm-a-Rest NeoAir UberLite REI Co-op Magma 15 vs NEMO Tensor Elite Ultralight Insulated REI Co-op Magma 15 vs Zpacks Solo Quilt 20F REI Co-op Magma 15 vs Nemo Tensor Ultralight