ACR Electronics Bivy Stick vs Fox 40 Micro Whistle

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

Fox 40 Micro Whistle is the lighter option — 90 g lighter than the ACR Electronics Bivy Stick (90% less weight). If grams matter to you, that is the one to beat.

Spec	ACR Electronics Bivy Stick	Fox 40 Micro Whistle
Weight	100 g · 0.100 kg · 0.22 lb	10 g · 0.010 kg · 0.02 lb
Brand	ACR Electronics	Fox 40
Category	Safety	Safety

ACR Electronics Bivy Stick

100 g

Compact two-way satellite communicator with SOS, GPS tracking and app-based messaging over the global Iridium network.

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Fox 40 Micro Whistle

10 g

Pealess safety whistle audible up to 1km.

Full details →

ACR Electronics Bivy Stick vs Fox 40 Micro Whistle: which should you buy?

If saving weight is your priority, the Fox 40 Micro Whistle wins — at 10 g it is 90 g (90%) lighter than the ACR Electronics Bivy Stick (100 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 safety page, or browse the full gear weight database.

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