In almost any engine from production to race, the ring pack will consist of two compression rings and a three-piece oil ring. The vast majority of rings are made of gray iron or ductile iron. Ductile is much tougher and the material of choice in high-performance applications. Either type can be moly coated, and nearly all ductile-iron rings are moly, but not all moly rings are ductile iron. Either way, a moly ring will really pay off in reduced bore wear over the long haul.