Robinson Racing 4331 64P Hard Coated Aluminum Pro Pinion Gear, 31T

"Pro" Pinions are precision machined from aircraft grade aluminum, lightened and coated twice with a super hard, black anodize. Recommended for onroad, but they can be run off road. Tooth number stamped on each pinion. 1/8 inch bore. One 5-40 set screw included. 1/16 inch allen wrench (not included) fits the 5/40 set screw.