... 20 to 34mm Weight: 106g Bicycle light Aluminum Mount instructions:* the mount adapt FEREI light such as P408N, F-V, ... F-VI, B3,B5,B9 * Loose the one side nut ... screw and inset the light through the hole . * Bicycle bar mount: Loose another nut screw ... down , it can be easy to mount on the bar , use the prepared 2 pieces ...