This is the Castle Creations 15T Mod-1 Pinion Gear for use on 1/8 Scale Cars. FEATURES: Steel construction Black in color INCLUDES: One 15T Mod-1 Pinion Gear One 3x4mm Set Screw REQUIRES: Fastening to motor shaft SPECS: Length: 12.4mm (0.49") Inner Diameter: 5mm (0.20") Castle CreationsPart CSE010-0065-09