If your accelerator pump shaft has worn the internal bore on your airhorn then this is the kit you need. What I provide is one smaller drill at 9/32" and then the finish drill at 5/16" along with the bushing that is required to bring the internal diameter back to the correct specifications for your shaft. The best way to drill this out is to set in a drill press with the drill bit perpendtiular to the airhorn. We realize that most do not have a drill press, the key is to drill the hole perfectly perpendtiular to the face of the hole. Bushing also sold on page without drill bits.