Professional Series forged racing pistons from Wiseco are no-expense-spared pistons designed for the serious racers and builders. Packed full of custom-level performance and durability features and provided with premium rings, Professional Series pistons are designed and built for use in heavy to severe duty race builds. Remove your limits with Wiseco?s Professional Series. Wiseco Honda K20A Piston Set, 86.50 mm Bore, 30.00 mm Compression Height, 0.866 in. Pin Diameter, Sport Compact, Set of 4. Honda K20A/Z