Part number: FCPPA830085RS4 Manufacturer: FCP Engineering Reinforced high-performance pistons for a variety of applications in almost all engine types for racing and street use. Made of 4032-T6 material, the bottom of the piston is molybdenum coated. Each piston kit also includes HD series rings and pins .Cylinder diameter: 83.00 mm Compression ratio: 8.5:1 Compression height: 30.80 mm Pin diameter: 22 mm Stroke: 92.80 mm Audi S4 RS4 - 3.0 30V Stroker Biturbo