This is the Castle Creations 32P 28T Pinion Gear for Monster Trucks. FEATURES: Aluminum construction INCLUDES: One 32P 28T Pinion Gear Two 2.5x3mm Set Screw REQUIRES: Installation on the motor shaft SPECS: Outer Diameter: 23.7mm (0.93") Hole Diameter: 5mm (0.20") Length: 12mm (0.47") Castle CreationsPart CSE010-0065-06