Part Number: FCPPA830090RS4STR1508 Manufacturer: FCP Engineering Forged high-performance pistons for a variety of applications in almost all types of engines for sport and street use. Made of 4032-T6, the bottom of the piston is molybdenum coated. Each piston set also includes HD series rings and pins. Cylinder diameter: 83.00mm Compression Ratio (CR): 9.0:1 Compression height: 30.80 mm Pin diameter: 22 mm Stroke: 92.80 mm Audi S4 RS4 - 3.0 30V Stroker Biturbo