GoPro mounting adapters set for bicycle carrier racks rear light/reflector mounting points. There are versions for two vertical holes and horizontal 50mm and 80mm bolt distances. They're straight forward to use, you need M6 hex bolts and nuts for the vertical holes version and M5 hex bolts and nuts for the both horizontal 50mm and 80mm version.
Special detail about the two vertical holes version is the peg in the bolt hole, that you're supposed to be able to remove and stick with superglue aka cyanoacrylate to the other hole under the adapter, or you can use very short or custom cut ~6mm diameter screw instead. It's purpose is to stabilize the adapter mount, since there's only room for one M6 bolt hole to keep the design compact.
Note: the structure or construction of your carrier rack may affect the suitability of these adapters for use, these are simple adapters that hopefully will work in most cases. You will quite likely need some kind of extension or another to position and adjust anything you may want to mount on the rack and you will find these extensions elsewhere.
CyclicDesigns
