The MTD 951-05156 Lawn Tractor Piston Ring Set is a key engine component that fits select lawn tractor models to maintain proper compression levels. It creates a tight seal between the piston and cylinder wall, allowing consistent combustion and limiting oil from entering the combustion chamber. This helps the engine run more steadily and minimizes smoke or oil loss during operation. ... https://www.wholetoolbox.com/mtd-951-05156-lawn-tractor-piston-ring-set