Robinson's Aluminum Pro pinions feature lightweight aluminum construction with an added hard coating that produces extra strenght and less friction. These pinions also feature a hollowed out core that reduces rotating mass for improv- ed acceleration and deceleration. Available in 48 pitch from 12 to 35 tooth sizes, and in 64 pitch in 16 to 47 tooth sizes. KPM 1/15/92 INCLUDES: 1 64pitch pinion 39 teeth 1 4-40 set screw REQUIRES: 0.050 size hex wrench such as GPMR8000. COMMENTS: This is the "Silencer Series" pinions.