The RAM-B-272 marine grade aluminium base consists of a 1" diameter ball and base with 9mm hole. This part is often used on motorcycles, attaching to the mirror frame, the main brand of bike for the RAM-B-272 is BMW. Material: Powder Coated Marine Grade Aluminium Ball Size: 1" Rubber Ball "B" Size TIP: Use this part on the Mirror Thread Insert on your Scooter to mount a Sat Nav. Just add an arm, base and holder to complete your mount.