This piston ring seals the combustion chamber between the piston and the cylinder wall in the host engine. It sits in the top groove of the piston and controls gas blow-by while managing oil consumption on the cylinder bore. A worn or broken ring causes compression loss, increased oil consumption, and visible exhaust smoke. The ring is manufactured to the original profile and tension specification, which maintains the correct contact pressure against the cylinder wall without excessive friction. On installation, ensure the ring gap is oriented away from the piston pin bore and that the ring is not over-expanded during fitting.