HydraPak UltraFlask+ 500ml vs SteriPen Adventurer Opti
Weight and specs compared for 2026 — and which one to choose.
Compressible 500ml soft flask with an integrated fast-flow filter cap. Built for trail running, fastpacking and on-the-move filtering from hydration vests.
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HydraPak UltraFlask+ 500ml vs SteriPen Adventurer Opti: which should you buy?
If saving weight is your priority, the HydraPak UltraFlask+ 500ml wins — at 65 g it is 25 g (28%) lighter than the SteriPen Adventurer Opti (90 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 hygiene page, or browse the full gear weight database.