Hastings, the OEM supplier to Harley-Davidson, manufactures these rings. They are the same piston rings that are shipped with every new motorcycle as well as sold by Harley's parts department. All ring faces are pre-lapped for easier seating. The exclusive Flex-Vent oil control ring is the easiest of all designs to install because there are no right side ups or side downs. The Flex-Vent ring also assures a uniform pressure on the cylinder wall contacting rails and a positive oil control. Its open design affords 200% greater drainage capacity than conventional designs. Even with all these features Hastings rings are made available by Zodiac at low, more affordable cost. These superb quality piston rings are sold in sets for two pistons with the exception of the XL 883 and XL 1100 Evolution Sportster rings, which are sold in single sets.