Speed Pro Flat Top Hypereutectic Piston is manufactured from aluminum alloy that contains 16 percent silicon for greater strength and wear resistance. Also molded in the latest permanent-mold technology to ensure the precise fit and tight bore clearances that today's top engine builders demand. It is ideal for use in high performance street, bracket, and oval track racing—and will work perfectly with normal ring end gaps. Bore: 4.040 inch. Stroke: 3.500 inch. Rod Length: 5.956 inch. Pin Diameter :0.912 inch. Piston Head Volume :+12.00cc.