A piston ring system, having an internal diameter >400 mm, for a piston of a two-stroke internal combustion engine, includes at least a first and a second piston ring each having a convex running surface with a crest of the convexity in contact with a cylinder wall and each being inserted into a respective first and second piston ring groove in the piston, wherein the first piston ring faces a combustion chamber and the second piston ring is disposed axially beneath the first piston ring, and wherein the crest of the convexity of the first piston ring is disposed beneath a radial plane passing through a midpoint of axial height of the first piston ring, and the crest of the second piston ring is disposed above a radial plane passing through a midpoint of axial height of the second piston ring.