Features:
【Durable & Light】Durable aluminum construction for long-lasting performance.
【More Fun】Provide the option of being able to change your gear ratio for different track conditions.
【Note】M1 is the pitch of each tooth on the pinion gear and the 12T 13T 14T 15T is the number of teeth on the pinion gear. You have to make sure your spur gear and pinion gear have the same pitch, or the teeth won't mesh.
【5mm】The pinion gear shaft diameter or bore is 5mm, make sure your RC motor shaft have the same diameter.
【Gear Combo Set】Comes with set screws for each pinion gear, the pinion gear combo set also included a hex key, easy to install.

Package include:
1 * M1 5mm 12T pinion gear
1 * M1 5mm 13T pinion gear
1 * M1 5mm 14T pinion gear
1 * M1 5mm 15T pinion gear
2 * 3.175mm to 5mm Converter
4 * Screws
1 * Hex key

Pay Attention: Make sure you thread lock the grub screw. They are hard to find when they fall out. Larger gears will result in higher speeds while smaller gears provide more torque. For quicker acceleration go for a smaller pinion gear (with fewer teeth) and a larger spur gear (with more teeth). Your car will accelerate off the mark very quickly with more torque, and you'll also benefit from cooler running temperatures, extending the life of your motor and ESC.