Piston rings are metallic, spring-driven seals installed within the grooves of a piston, sealing the combustion chamber within an internal combustion engine. These rings primarily control oil consumption, maintain compression, and transfer heat from the piston to the cylinder wall. Common ring types include compression rings, oil control rings, and scraper rings, each designed with specific cross-sectional shapes and materials for optimized performance. Materials typically consist of cast iron, ductile iron, or steel alloys, often with surface coatings like chrome, moly, or plasma spray to reduce friction and wear. Proper ring end gap and installation orientation are critical for sealing and longevity. Failure manifests as excessive oil consumption, reduced power, and increased emissions.