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Sea to Summit Spark SP III vs Therm-a-Rest Vesper 32°F Sleeping Bag

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

Therm-a-Rest Vesper 32°F Sleeping Bag is the lighter option — 159 g lighter than the Sea to Summit Spark SP III (22% less weight). If grams matter to you, that is the one to beat.
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Spec Sea to Summit Spark SP III Therm-a-Rest Vesper 32°F Sleeping Bag
Weight 709 g · 0.709 kg · 1.56 lb 550 g · 0.550 kg · 1.21 lb
Brand Sea to Summit Therm-a-Rest
Category Sleep System Sleep System
Sea to Summit Spark SP III
709 g

850-fill down sleeping bag rated to 0°C / 32°F.

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Therm-a-Rest Vesper 32°F Sleeping Bag
550 g

Premium ultralight sleeping bag with 900-fill hydrophobic goose down. Rated to 32°F (0°C) with mummy fit and draft collar for warmth retention.

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Sea to Summit Spark SP III vs Therm-a-Rest Vesper 32°F Sleeping Bag: which should you buy?

If saving weight is your priority, the Therm-a-Rest Vesper 32°F Sleeping Bag wins — at 550 g it is 159 g (22%) lighter than the Sea to Summit Spark SP III (709 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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