#35 Sprocket For Wheel 40 Tooth Hardened Recommended for use with 13 tooth shaft sprocket to keep 3 to one factory gear ratio on Cobra, The Rock, Nuke, Lowrider Rock & StandR This sprocket will increase speed on all other models using 4 to 1 gear ratios, such as SCOOTR, Raser or or Rockville or Libra or StarII or Salorr with 9 inch rear tire. But is not recommended with 3.0-4/280x65 rear tires unless you don't care about hill pulling ability or potentially straining your clutch. Recommended wheel sprockets for 10 inch rear tires would be 45 tooth only. "Big wheel" models use 60 tooth wheel sprockets.