18T Mod-1 Pinion Gear for use on 1/8 and 1/10 Scale Cars that use Mod 1 Gearing. FEATURES: Hardened steel constructionBlack in colorYOU WILL RECEIVE: One 18T Mod-1 Pinion GearOne 4x4mm Set ScrewREQUIREMENTS: Installation onto the vehicleSPECIFICATIONS: length: 12mm (0.47")Inner diameter: 5mm (0.20") description revised by: WP February 12, 2014