In terms of mass, the pistons of one engine should not differ from each other by more than±2.5 g.
If there is no set of pistons of the same weight group, you can remove a part of the metal on the basis of the bosses under the piston pin. The place of removal of the metal is indicated by arrows in fig. 2-30. Metal removal, however, must not exceed 4.5 mm in depth relative to the nominal piston height (59.40 mm), and the width is limited to a diameter of 70.5 mm.