This is the 15T 5mm Pinion Gear from Ofna. FEATURES: Steel construction Fits 5mm motor shafts INCLUDES: One 15 tooth Pinion Gear One 4x4mm Set Screw REQUIRES: Installation on the motor SPECS: Length: 14mm (0.55") Inner Diameter: 5mm (0.20") Outer Diameter: 17mm (0.67") cnh 4/8/10 ir/jxs