This is an optional Team Integy 40 Tooth Steel Spur Gear for the Traxxas Revo. FEATURES: Steel Construction Black in Color INCLUDES: (1) Steel Spur Gear (3) 3x8mm Round Head Machine Screws REQUIRES: Installation SPECS: Teeth: 40 Outside Diameter: 1.665" (42.2mm) Inside Diameter: 0.427" (10.8mm) IntegyPart INTT3219