These components are circular metal pieces installed between a vehicle’s wheel hub and wheel. They effectively increase the track width, the distance between the centerline of the wheels on the same axle. As an example, fitting these components to a pickup can alter the stance of the vehicle.
The utilization of these parts can offer several advantages, including improved aesthetics by pushing the wheels outward for a more aggressive appearance. Functionally, they can sometimes enhance handling characteristics by widening the vehicle’s base. There are specific applications where they are necessary to provide clearance for larger tires or aftermarket brake systems. Originating from motorsports and off-road applications, the adaptation to street vehicles grew, fueled by a desire to customize vehicle appearance and performance.