This tool is designed to allow you to quickly check that the upper trailing arm bushings on your stock style housing are level to one-another. Many sanctioning bodies have this requirement in their rules package. The base has magnets that allow the guage to stick right on to your axle tube. A thumb screw on the pointer allows quick adjustment. Simply set this guage to the center of the pivot on one side, remove it and place on the opposing axle tube and you have a quick check of your pivot heights relative to eachother. A must have for any racer or tech official.