【Compatible with】Universal Mod 1 pinion gear, Inner Diameter : 5mm, For motor shaft diameter : 5mm. Make sure your RC motor shaft have the same diameter. 【Material】CNC machined. Made of high quality Hardened Steel to increased wear resistance and improve fatigue life, make them roll smoothly. 【Suittable for】Fit for 1/8 Arrma Kraton Losi Trxs Axial Redcat RC Trucks Buggy brushed brushless motor. It is good choice for RC Car fans. 【NOTE】Increase your speed safely and avoid overheating issues by starting with the smallest tooth size 5mm pinion gear and gradually moving up to larger sizes 5mm pinion gear. Throughout the run, make sure to monitor the temperatures of your ESC and motor, so you can adjust your speed and avoid any potential damage or malfunctions. 【Compatible with】Universal Mod 1 pinion gear, Inner Diameter : 5mm, For motor shaft diameter : 5mm. Make sure your RC motor shaft have the same diameter.