This is the ST Racing Concepts Silver Aluminum Oversized Rear Hub Carrier with Bearings. Using high quality CNC machined aluminum, these oversized Aluminum rear hub carrier greatly increase the strength of your rear suspension, while adding great looks to your Traxxas electric Slash, Bandit, Rustler, Stampede, and Monster Jam. Because of the increase in size of bearing for durability, we have included a full set of 5x11mm ball bearings (replacing the stock 5x9mm bushing) for improved efficiency of the rotating axle and durability.