Mahle Motorsport Piston Set for BMW S52 engine. 86.60mm Bore, 89.6mm Stroke, 135mm Rod, 22mm Pin. Choose 12.5:1, 11.2:1, or 9:1 CR for N/A or Forced induction applications. CR calculated at 0.8mm above deck and 1.73mm head gasket thickness. PowerPak Plus 2618 Alloy & Hard Anodized Top Ring Groove For Extreme Duty Applications.