The adjustable tubular lower trailing arms are made of 1 ¼” x .093” chrome moly. These units are a direct replacement for the OEM arms and come complete with chrome moly heim joints. McDonald Bros Racing are now supplying diff bracketry to replace the original bracketry on the Holden Commodore. They then can be set up with adjustable coilover shockers to replace the original suspension for optimum control.