Supplied in the following major brands: Dunlop & Challenge. HTD 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. Sizes range from 12-5M-15 - 72-5M-15, other sizes may also be available but may not be displayed please contact us if you require a size not displayed on our shop.