32 pitch alloy pinions are not heat treated and should only be used with plastic spur gears. If you only run plastic spur gears these pinions are the perfect choice. 32 pitch Alloy Pinions are not stamped with tooth number. 1/8 inch bore. One 5-40 set screw included. 1/16 inch allen wrench (not included) fits the 5/40 set screw.