This is the 11T Mod-1 Pinion Gear from Castle Creations. / / FEATURES: For 1/8 scale cars / Steel construction / Black in color / / INCLUDES: One 11T Mod-1 Pinion Gear / One 4x4mm Set Screw / / REQUIRES: Installation on the vehicle / / SPECS: Length: 12mm (0.47") / Outer Diameter: 12.75mm (0.50") / Inner Diameter: 5mm (0.20") / Tooth: 11