The "Pro" Pinions are precision machined from aircraft aluminum, lightened and then they're coated twice with a super hard, black anodize. Recommended for onroad, but they can be run off road. Pinions (14 thru 35) stamped with tooth number. 1/8 inch bore. One 5-40 set screw included.

Outer Diameter: 21.65mm (0.85")
Inner Diameter: 3.15mm (0.12")