The "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. A wide selection
of tooth sizes is available (see below for sizes). 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.