It is highly recommended, but not mandatory, that you send along a new piston to most accurately set your final piston-to-wall clearances. Please do not send the ring(s); we measure your piston from the skirt and do not require the rings for processing. If you do not send a piston, please specify the final bore size for us on the work order form. If no sizing information or piston is sent, we will assume you want the bore restored to original factory bore size. US Chrome is a dealer of Wiseco, Pro-X, SPI, Wossner and other aftermarket pistons. Do not hesitate to contact us for competitive piston prices!