Imprial Pilot Bore Timing Pulleys, 3/8" Pitch for 1" wide Belt.

Imperial timing pulleys have equally spaced grooves machined in to the outside diameter, to give correct meshing with the belts teeth, The pulley grooves are of special design to give this correct meshing of the belt teeth with minimal friction.
All pulleys manufactured have correct minimum meshing tolerances built in and the pitch diameter is always larger then the outside diameter.