Speedometer gearbox / drive, Right hand (drives from bottom of axle when on RH side) suit magnetic speedo. 15:12 / 1.25:1 ratio, mounts on rear axle, rounded ends 11/16 " hole, suits Norton Commando Mk3. BG5330-170Suits many bikes after 1966 :BSA A65S/T, B44 Enduro Special, BSA Rocket 3 1971-72, Norton Commando 750/850 1969-74, Triumph T120/TR6 T150 1971-74, T140 1973-78.OEM number: 19-9217; 19-2225;Norton 06-0627, 060627Triumph: 60-0637; 60-1979; 99-9994; 90-3213