To compliment our Scorpion HK series Helicopter motors, we are now offering Pinion Gears in the popular Mod .5 size that are used with most 400, 450 and 480 class electric helicopters. These pinions are designed to fit any motor with a 3.175mm shaft (1/8 inch), and come with an allen key set screw. This package includes one 10-Tooth pinion gear and one set screw. Innov8tive Designs