Wossner is Germany's finest aftermarket forged piston and rod manufacturer and have over 25 years of experience in the high-performance racing industry. Top European racers and FIM World Champions rely on Wossner for only the best pistons, rods and customer service.Features In-house designed and manufactured; all forgings are produced in Wossner's company-owned forging operation 4-stroke pistons are made using a double-bridged forging design Lightweight pistons with the tightest piston-wall clearances in the industry give you a quieter running engine All pistons include piston, ring, wrist pin and pin locks Wossner pistons are used by leading Supercross, Arenacross and MX GP teams Made in Germany Specifications Piston Size: 76.96mm Oversize: Standard Wossner Compression: 12.80:1 OEM Compression: 12.50:1 Number of Rings: 2 Replacement Rings: RIK77.00D Replacement Wrist Pin: WP070 Replacement Circlip: CW16 Fits: Yamaha WR250F 2001-2004 YZ250F 2001-2004