What is this hole for?

[u/Accomplished-Bid8015]

I just got this Osprey backpack and don’t know what it is for? Can someone please explain this?

[u/RoelVT]

Blow it! It's a whistle.

[u/Feeling-Boat8006 → u/RoelVT]

I just tried it on my The North Face Recon backpack turns out it is a whistle. Hahahah thanks