Part Number: FCPPA820085RS4STRManufacturer: FCP EngineeringForged high performance pistons for a variety of applications in almost all types of engines for racing and street use.Made of 4032-T6 material, molybdenum coated piston bottom.Each piston set also includes HD series rings and shafts.Cylinder diameter: 82.00 mm Compression Ratio (CR): 8.5:1 Compression height: 27.50 mm Shaft diameter: 21 mm Piston stroke: 92.80 mm Audi S4 RS4 - 3.0 30V Stroker Biturbo