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.
Used with permission, copyright 2019 Robinson Racing Products/Horizon Hobby, Inc,. Copyright 2019 Brey Corp. t/a Hobby Works