This is the Robinson Racing 32 Pitch 9 Tooth Pinion Gear.
FEATURES: Standard alloy 32 pitch pinion gears are a great replacement for many
Kyosho cars and any cars that use 32 pitch pinion gears
INCLUDES: One Robinson Racing 32 Pitch 9 Tooth Pinion Gear with set screw
SPECS: Inner Diameter: 1/8" (3mm) Outer Diameter: 0.33" (8.5mm)