Mahle OE plasma-moly top compression ring set in 4.005" diameter by .0625" thickness with .190" RW measurement. The description specifies a steel top compression ring treated with plasma moly for wear resistance and direct-fit replacement where the 4.005 x .0625 specification is needed. It’s intended for rebuilds that demand precise ring sizing and surface finish.
Mahle Rings Performance Plasma Moly Steel Top Compression Ring 4.005 x .0625 .190 RW Moly Ring Set