This is the Associated 72 Tooth 48 Pitch Spur Gear for the RC10B4 and RC10T4.
These spur gears are for gear ratios used with 17.5, 13.5 and 10.5 brushless stock motors and allows the use of smaller sized pinion gears. This spur gear moves motor forward for better balance and more predictable handling.
One Spur Gear
Requires: Installation on the vehicle
Outer Diameter: 40mm (1.6")
Inner Diameter: 4.8mm (0.19")
Width: 5.2mm (0.20")