Sea to Summit Spark Pro Down 30 vs Western Mountaineering Ultralite 20°F

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

Sea to Summit Spark Pro Down 30 is the lighter option — 61 g lighter than the Western Mountaineering Ultralite 20°F (9% less weight). If grams matter to you, that is the one to beat.

Spec	Sea to Summit Spark Pro Down 30	Western Mountaineering Ultralite 20°F
Weight	619 g · 0.619 kg · 1.36 lb	680 g · 0.680 kg · 1.50 lb
Brand	Sea to Summit	Western Mountaineering
Category	Sleep System	Sleep System

Sea to Summit Spark Pro Down 30

619 g

Ultralight mummy bag rated to 30F (-1C) with 950+ fill-power Ultra-Dry Down. 10-denier shell, shoulder and footbox zippers for temperature control.

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Western Mountaineering Ultralite 20°F

680 g

Premium 850-fill down sleeping bag rated to 20°F (-7°C).

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Sea to Summit Spark Pro Down 30 vs Western Mountaineering Ultralite 20°F: which should you buy?

If saving weight is your priority, the Sea to Summit Spark Pro Down 30 wins — at 619 g it is 61 g (9%) lighter than the Western Mountaineering Ultralite 20°F (680 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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