Hastings 3.750 Moly Piston Ring Set For Harley Twin Cam Features All ring faces are pre-lapped for easier seating and, in the moly sets, the compression ring features a moly insert on its barrel face design Exclusive Flex-Vent oil control ring is the easiest of all designs to install because there are no right sides up or down It can't overlap, can't gouge and can't be installed wrong The 80-plus shoulders on the die-formed stainless-steel stress-relieved spacer/extender exerts uniform pressure on the rails for positive oil control Open design affords 200 greater drainage capacity than other designs