These pistons are specifically designed for Big Duke/Big Chief cylinder heads and feature our race proven dome and skirt design. Valve reliefs are designed to accept oversized valves and long duration, tight lobe separation roller cams. Precision CNC machined ring grooves accept .043 D-wall, 1/16, 3/16 rings. Includes: Pin #990-2930-15-51S (150g) Forced pin oiler, with annular oil reservoir. Bore: 4.600 Stroke: 4.250 Rod: 6.385 Deck: 9.780 Price per piston.