This is an adaptor to convert a GoPro mount (either side) to a standard 1/4-20 tripod mount.
A 3/4 inch 1/4-20 bolt is pressed into the mount base and a 1/4-20 screw can be glued into the thumb screw handle. If you also need the screw to attach the two ends of the GoPro adaptor, @tmorris9 has a nice model here: http://www.thingiverse.com/thing:163883
The nut that connects the two sides of the GoPro mount is a M5 end cap nut.
The author marked this model as their own original creation. Imported from Thingiverse.