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Sea to Summit Spark SP I vs Therm-a-Rest Hyperion 20F/-6C (Regular)

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

Sea to Summit Spark SP I is the lighter option — 170 g lighter than the Therm-a-Rest Hyperion 20F/-6C (Regular) (30% less weight). If grams matter to you, that is the one to beat.
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Spec Sea to Summit Spark SP I Therm-a-Rest Hyperion 20F/-6C (Regular)
Weight 397 g · 0.397 kg · 0.88 lb 567 g · 0.567 kg · 1.25 lb
Brand Sea to Summit Therm-a-Rest
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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Therm-a-Rest Hyperion 20F/-6C (Regular)
567 g

Ultralight 20F down mummy bag with 900-fill Nikwax Hydrophobic Down for fast-and-light backpacking.

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Sea to Summit Spark SP I vs Therm-a-Rest Hyperion 20F/-6C (Regular): which should you buy?

If saving weight is your priority, the Sea to Summit Spark SP I wins — at 397 g it is 170 g (30%) lighter than the Therm-a-Rest Hyperion 20F/-6C (Regular) (567 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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