This is the 38 Tooth and 13 Tooth Final Gear Set for the Nitro RS4 MT Kit. FEATURES: Replaces worn or damaged final gears. YOU WILL RECEIVE: One Steel 38 Tooth Final Gear One Steel 13 Tooth Final Gear REQUIREMENTS: Attaching to differential case with four screws (not included). SPECIFICATIONS: 38T Diameter: 1.42" (36mm) 13T Diameter: .543" (14mm) cmc 2/11/01 ir/jl &