Got the gopro second hand, and I was desperate por extra ports.
Please do not make the same mistake I made trying to open this small "door". Not really a door, it is a water drain system for the microphone.

If this happens to you, no worries, this small door is just a water drain. If you break it open it won't break anything in the camera, waterproof will still work because the water drian didn't cover the microphone membrane in the first place.

To fix it just put glue on the parts that had glue and don't put glue on the microphone membrane (circle under the water drain) and you will be fine, it wont affect the functionality.

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