gregconquest 5 Official GoPro screws are 19mm long, but 20mm fits OK in my devices. So, M5x20 works OK; it uses a 3mm hex wrench. You could add a washer if some devices don't fit exactly. ...The M5x30 does not work well, though. The threaded portion is about 23mm long, and a normal washer won't help because the unthreaded portion is the same 5mm diameter as the threaded portion. It uses a 4mm hex wrench, FWIW.