Aluminum sealed differential case with hardened steel cog differential gear for the Traxxas Stampede, Rustler, Bandit, 2WD Slash, and monster Jam vehicles features: conk aluminum sealed differential case hardened steel gear sealed differentials allows you to tune to current track conditions by changing the weight of the diff oil. Four O-rings help Seal against fluid leakage which results in a very smooth differential that improves the performance of your vehicle. You will receive: one sealed differential case ( no gears inside ) requirements: filling diff fluid and assembling the diff case with stock Traxxas diff gear installation on the vehicle specifications: outside diameter: 37.5mm (1.48 ) shaft diameter: 5.10mm (.200 ) overall thickness: 21.2mm (.834 ).