The present invention relates to a piston for a cartridge for a drug delivery device comprising: at least one annular sealing surface to radially abut against an inner side wall of a cartridge, a distal surface to confine a drug receiving volume of the cartridge, a thrust receiving surface adapted to receive a thrust exerting plunger of a drug delivery device for displacing the piston in a proximal direction relative to the side wall, wherein the thrust receiving surface comprises numerous centering elements protruding from the thrust receiving surface towards the plunger and wherein the centering elements comprise an outer shape and geometry that matches with a corresponding receptacle of the plunger, and wherein the centering elements are arranged and aligned on the circumference of an imaginary annular or circular structure.