Fits diameter 25 mm. Threaded holes (M4x12) for holder attachment. For installation of devices on pipes and rods/bars, for example most types of vehicles; motorcycles, boats, carts, stands, wheelchairs, airplanes etc. The mount has threaded holes in a round multiple AMPS-pattern. The holes are for M4x12 screws. The mount fits pipes with diameter 25 mm.