This is a 41 Tooth Nitro Spur Gear by HPI FEATURES: Black nylon construction, one-way bearing type spur gear YOU WILL RECEIVE: One 41 Tooth Nitro Spur Gear One Gear ratio chart and installation guide REQUIREMENTS: HPI Nitro Two-speed transmission or one-way bearing COMMENTS: This will only work with a one-way bearing, will not work properly with 1st gear adapter. The included gear ratio chart list recommends gears for specific HPI vehicles. dab 10-18-01 ir/kh &