This is a 47 Tooth 2-Speed Spur Gear by HPI for the the Nitro 3. Replaces old or worn 2-Speed Spur Gears. Hard Plastic Construction Black in Color One 47 Tooth Spur Gear Removing Worn Gear and Replacing with New One. Teeth: 47 Diameter: 14.5mm or 0.574" (Inside) EEW 6/7/02 ir/kh &