Grand National GN6R forged aluminum six-piston radial mount calipers bring current state-of-the-art design, materials, and manufacturing technology to this long standing icon in the Wilwood caliper line. With a High-strength forged aluminum body in either hard-anodized or Quick-Silver nickel plate finish and Compatible with rotors from 1.25†to 1.38†thickness and diameters from 12.19†to 13.06â€. Two body widths are available for use with .80†(20,3) or .99†(25,0) thick pads. Stainless steel pistons are included base model GN6R anodized calipers and Thermlock® pistons in the GN6R/ST models. Uses 3.5†or 6.0†center mount bracket kits to replace all previous Grand National caliper models.