Ultra high quality NPR piston ring set for BMW S54 piston (as found in E46 M3, late Z3 M and Z4 M models). Includes top ring, middle ring and oil control ring set. NPR are the industry standard for quality piston rings. These rings are a perfect addition to any engine rebuild. Specified for original 87mm bore and original BMW pistons. Priced per piston (quantity of six required per engine).