Three types for you to choose, one is compatible for Garmin, and one is for Bryton, and the last type is for CATEYE. The Screw Hole Distance: Approx. 21mm / 0.8in(The adapter for Garmin, Bryton). Applicable Common Screw Type & Length(Not included): M3, 6mm / 0.24in(for Garmin, Bryton ), M3, 10mm / 0.39in(for CATEYE).