Do I need to supply a piston?

No. If a piston is supplied or purchased from us, we will custom fit the bore and piston clearance. If no piston is supplied, we restore the cylinder to the OEM bore size. If you would like to purchase a piston (Wiseco, Vertex, JE, Pro-X, SPI , Wossner, and other major brands are available at a competitive price), we custom fit the bore and piston clearance.