This is conversion kit to change your Powermatic 66 from the old 3 belt drive to a 2 belt drive. Powermatic discontinued the sheaves years ago and has not offered an alternative. If you have a 3600 rpm motor this will spin it at 4860 rpm at the arbor. This is well within the rpm ratings for 10 blades. The motor pulley is 7/8″ bore with a 3/16″ key, and the arbor pulley is 3/4″ bore with a 3/16″ key. It also includes a new set of drive belts.