The 48 pitch hard nickel plated alloy steel pinions are precision cut gears that last and last when used with a plastic spur gear. In sizes 12 through 40 teeth. Pinions stamped with tooth number. The bright nickel finish protects the steel from corrosion and increases lubricity of the gear by reducing friction and adhesion between the pinion and spur gear. 1/8 inch bore. One 5-40 set Screw included. 1/16 inch Allen wrench (not included) Fits the 5/40 set screw.