HydraPak 42mm Filter Cap vs SteriPen Adventurer Opti

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

HydraPak 42mm Filter Cap is the lighter option — 33 g lighter than the SteriPen Adventurer Opti (37% less weight). If grams matter to you, that is the one to beat.

Spec	HydraPak 42mm Filter Cap	SteriPen Adventurer Opti
Weight	57 g · 0.057 kg · 0.13 lb	90 g · 0.090 kg · 0.20 lb
Brand	HydraPak	SteriPen
Category	Hygiene	Hygiene

HydraPak 42mm Filter Cap

57 g

Lightweight fast-flow filter cap that threads onto 42mm bottles, removing bacteria and cysts for hiking and travel.

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SteriPen Adventurer Opti

90 g

UV water purifier. Purifies 1L in 90 seconds.

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HydraPak 42mm Filter Cap vs SteriPen Adventurer Opti: which should you buy?

If saving weight is your priority, the HydraPak 42mm Filter Cap wins — at 57 g it is 33 g (37%) 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.

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