This is quite custom mount ideally suitable for mounting GoPro Session behind the scope, using picatinny rail.
It was designed to sit on Hatsan Gladius airgun, with Leapers UTG Compact 3-12x44 30 mm AO MilDot EZ-Tap scope. Still, it may be relevant for other setup as well.
There is a thin plate included in the bottom of design that links main body with GoPro link section, to prevent small elements moving around on the table in beginning. This should be cut off after printing.