Deep Spiral Angle bevel gear set for the 1/16 Traxxas 4 wheel drive. These mount inside the front and rear transmission. FEATURES: CNC hardened steel and aluminum construction A deep spiral angle spiral bevel gear is a gear with helical teeth formed along spiral lines on the gear face. the main advantage of spiral gears over straight gears is the smoothness of operation as the teeth engage more gradually. the contact between the teeth starts at one of the tooth and spreads across the entire tooth. the result is a much smoother transfer of force when each pair of teeth comes into contact. YOU WILL RECEIVE: one ring gear set one pinion gear Two pieces of shim. (might or might not use all of it) REQUIREMENTS: Two sets per vehicle Best use the with a new TRA3030X or TRA3029X. Must shim the gear mesh (you might or might not use the shim pending your transmission case) COMMENTS: Shimming the differential correctly is an important step and this is the building the perfect gearbox. If you need more you can purchase Hot Racing part number W8X. This does not include inner differential gears.