[Suitable For] 5mm/3.175mm shaft size motors, compatible with Arrma, Axial, Redcat 1/8 and 1/10 scale RC car trucks. [What You Get] Includes 5 pieces of pinion gears (14T, 15T, 16T, 17T, 18T), grub screws for each gear, an L-shaped hex key for easy installation, and a 5mm to 3.175mm shaft coupler to allow your Mod 1 5mm pinion gear to fit 1/10 RC car motors. [Note] To increase speed safely and avoid overheating, start with the smallest tooth size 5mm pinion gear and gradually move to larger sizes. Monitor the temperatures of your ESC and motor during operation to prevent potential damage or malfunctions. [Hardened Steel 5mm Pinion] Constructed from high-quality hardened steel, these pinion gears offer durability and strength for a reliable RC racing experience. Designed for reuse and resistant to wear from continuous use, they provide long-lasting performance. [Compatibility] For proper fit, ensure both the pinion gear bore and motor shaft diameter are 5mm. M1 pitch determines the spacing between gear teeth; it is essential to match the pinion gear pitch with that of the spur gear to ensure proper meshing and prevent operational issues. Quantity: 5PCS Color: Black Material: Metal Package Contents: 1 x RC Car Mod 1 Pinion Gear Kit (only the items listed above; other products not included) Note: Lighting and display differences may cause slight color variations between the image and the actual item. Measurement may vary by +/- 1-3cm.