These S&S 1250cc conversion pistons for 1986-'21 HD® Sportster® Models increase the displacement of 883cc and 1200cc engines to 1250cc at 11.2:1 compression. May be used with stock 1200cc cylinder heads, but S&S CNC ported heads are recommended. Stock 1200cc cylinders and 1986-'2003 883cc cylinders may be bored to accept the 3-9/16" bore 1250cc pistons, but 2004-'16 883cc cylinders may not be used. Also available in a cylinder and piston kit.