This is a 45 Tooth Two Speed Spur Gear for the HPI Nitro RS4 3. FEATURES: Black nylon construction YOU WILL RECEIVE: One 45T gear One installation sheet REQUIREMENTS: Installation onto Nitro RS4 3. SPECIFICATIONS: Outer diameter: 47mm (1.85") Thickness: 5.2mm (0.21") Number of teeth: 45 Pitch: 1M cmc 11/11/02 ir/kh &