4 Aluminum Pistons, 2 Piece Aluminum Body XA2.E7 Series 4 Piston GT Road Race Calipers Typical GT, GTU & GT1 Front or Rear Caliper Lightweight and Rigid 4 Aluminum Pistons 2 Piece Aluminum Body 130mm Radial Mount Centers with 62mm Offset Disc Diameter 332mm to 355mm