Part Number: FCPPA845085RS6 Manufacturer: FCP Engineering Forged high performance pistons for a variety of applications in almost all engine types for racing and street use. Made of 4032-T6, the bottom of the piston is molybdenum coated. Each piston kit also includes HD series rings and pins. Cylinder Size: 84.50 mm Compression Ratio (CR): 8.5:1 Compression height: 30.70 mm Pin diameter: 21 mm Stroke: 93.00 mm Audi RS6 C5 - 4.2 40V V8 Biturbo (BCY, BRV)