Sea to Summit Ultralight Insulated vs Zpacks Classic 20°F Sleeping Bag

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

Zpacks Classic 20°F Sleeping Bag is the lighter option — 19 g lighter than the Sea to Summit Ultralight Insulated (3% less weight). If grams matter to you, that is the one to beat.

Spec	Sea to Summit Ultralight Insulated	Zpacks Classic 20°F Sleeping Bag
Weight	595 g · 0.595 kg · 1.31 lb	576 g · 0.576 kg · 1.27 lb
Brand	Sea to Summit	Zpacks
Category	Sleep System	Sleep System

Sea to Summit Ultralight Insulated

595 g

Insulated inflatable pad with R-value 3.7.

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Zpacks Classic 20°F Sleeping Bag

576 g

Ultralight mummy sleeping bag with 900-fill power goose down rated to 20°F. Water-resistant down and Dyneema shell. Weighs 20.3 oz in regular size.

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Sea to Summit Ultralight Insulated vs Zpacks Classic 20°F Sleeping Bag: which should you buy?

If saving weight is your priority, the Zpacks Classic 20°F Sleeping Bag wins — at 576 g it is 19 g (3%) lighter than the Sea to Summit Ultralight Insulated (595 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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