Marmot Plasma 15°F vs Western Mountaineering AlpinLite 20

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

Marmot Plasma 15°F 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	Marmot Plasma 15°F	Western Mountaineering AlpinLite 20
Weight	850 g · 0.850 kg · 1.87 lb	879 g · 0.879 kg · 1.94 lb
Brand	Marmot	Western Mountaineering
Category	Sleep System	Sleep System

Marmot Plasma 15°F

850 g

800-fill down sleeping bag rated to 15°F (-9°C).

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Western Mountaineering AlpinLite 20

879 g

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

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Marmot Plasma 15°F vs Western Mountaineering AlpinLite 20: which should you buy?

If saving weight is your priority, the Marmot Plasma 15°F 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.

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