Gearbox sprocket for the BSA C15 and B40 trials models. These are suitable for use with a 428 chain. Available with 13 or 14 teeth. Please note these sprockets are much smaller than standard, and your chain may foul the standard sprocket lock nut. If this is the case, you will need to make alteration to the locknut until it clears the final drive chain. **APOLOGIES WE ARE OUT OF STOCK OF 13 TEETH**