GoolRC 5Pcs 32DP 5mm 13T 14T 15T 16T 17T Motor Pinion Gear Combo Set for 1/10 RC Car Brushed Brushless Motor Suitable shaft diameter: 5mm Hard anodized on the gear surface Rust-proof treatment on the surface of gears The gears are milled by precisely Tanwai milling machine A M4 set screw(12.9 level)has been added to each pinion gear