Product Description: SUBARU IMPREZA (GR,GH,GJ) WRX STi FRONT PERFORMACE DIMPLED GROOVED BRAKE DISCS + BREMBO PADS SET Brake Disc Type:Internally Vented | Dimpled Grooved Brake disc diameter: 326mm Brake Disc Thickness: 30mm Brake Disc Minimum Thickness: 28mm Centering Diameter: 58mm Overall Height: 52.08mm 100 pcd Kinetix Sports Performance Brake Discs: Dimpled Grooved: The key benefits of the dimpled and grooved discs are that brake fade is significantly reduced. the science behind this is the dimples and the grooves deglaze the pad and vents gasses that build up between disc and pad during braking. The additional slots dissipate heat more effectively, thus greatly reducing the risk of deformation, vibration or cracking of the disc .