Sea to Summit Spark SP I vs Zpacks Sleeping Bag 20°F

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

Both weigh the same at 397 g, so choose on features, price and fit.

Spec	Sea to Summit Spark SP I	Zpacks Sleeping Bag 20°F
Weight	397 g · 0.397 kg · 0.88 lb	397 g · 0.397 kg · 0.88 lb
Brand	Sea to Summit	Zpacks
Category	Sleep System	Sleep System

Sea to Summit Spark SP I

397 g

Ultralight 850-fill down sleeping bag rated to 25°C.

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Zpacks Sleeping Bag 20°F

397 g

Ultralight 900-fill down sleeping bag rated to 20°F.

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Sea to Summit Spark SP I vs Zpacks Sleeping Bag 20°F: which should you buy?

On weight these two are identical (397 g), so your decision comes down to features, fit and price. Check the full details and current price for each above.

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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