This is an adaptor to fit 52mm photography lenses to a GoPro Hero5, Hero 6 or Hero 7.

Push the adapter over the lens protector of the GoPro and then screw in your desired 52mm lens. I used PET-G, the thread will probably feel quite tight to begin with- be gentle, its fairly easy to cross thread. After fitting a few times, it should ease up a little.

I've incorporated a grub screw hole in the bottom to keep it on the GoPro although the fit is fairly snug. Using a grub screw may cause a slight mark on the edge of the lens protector but it will keep the adapter fixed in place.