Bought an adapter from PhoneSkope.com to use your GoPro Hero 3+/4 and ended up buying a Hero 5 Black later, only to be upset that Phone Skope doesn't sell an adapter for the Hero 5? Don't want to have to print out my entire GoPro Hero 5 Black Scope / Optic Adapter and really only need a little adapter to use your Hero 5 with your current plate? Well, you're in luck today! This will fit around your Hero 5 Black's lens, making it the same size as the Hero 3+/4's (of course, I'm talking about the case's lens, not the round camera lens). This should work with any other GoPro Hero 3+/4 accessories where you use a friction fit of the case's lens to mount the camera.
Designed in Fusion 360, but I'm not including the F360 file as I don't think it's needed. The external dimensions are 36.3mm x 33.8mm with a corner radius of 3.5mm. The Hero 5's lens dimensions are 32mm x 28.75mm with a corner radius of 5mm. I then offset that 1.9mm to create a hard stop for the lens. It's extruded 5.5mm (the stop is only 1mm).
Pretty simple stuff here, folks. I hope this solves a problem for you! Enjoy!