350 Chevy Moly Ring set4.040 bore5/64 5/64 3/16 Grove SizeMAHLE, manufacturer of Perfect Circle piston rings, is the largest manufacturer of piston rings in the world, leads the way in ring technology and innovation. Perfect Circle rings are at the forefront of both light and heavy vehicle piston ring technology. Extensive OE connections mean that Perfect Circle rings have the technological edge. Things like the CP-20 oil ring, narrow compression rings, steel compression rings for gasoline engines, low tension oil rings and coated compression rings for diesels all came from the OE. Now, MAHLEs rededication to the Perfect Circle performance line proves that Perfect Circle should be the ring choice under every hood - regardless of the application.