Abstract: A method and apparatus for sizing a piston to a defined size outer diameter surface, which is the contact surface with the cylinder of an internal combustion engine. The apparatus method involves first measuring each piston, then calculating the amount of coating required to achieve the desired diameter for each individual piston or range of pistons and then applying a precise coating in either one or more coats preferably by using a rotary pad printing technique to produce the precise film thickness, thus narrowing the diameter range of the group of pistons.