Abstract: A durable piston is applied in a cylinder of an engine to output internal exploding power and has a piston head and a durable ring unit. The piston head is mounted in the cylinder of the engine, is driven for outputting kinetic energy and has a ring unit mount. The durable ring unit is mounted around the ring unit mount and has a distal ring and a proximal ring. The rings are mounted around the ring unit mount. An inner edge of the distal ring and the proximal ring are separated from the piston head of the piston so forming a first airway and a second airway. When the engine operates, high-pressure air fills the airways and presses the rings against the cylinder. Consequently, the airways maintain contact between the durable ring unit and the cylinder tight to prevent air leakage.

Abstract: A durable piston is applied in a cylinder of an engine to output internal exploding power and has a piston head and a durable ring unit. The piston head is mounted in the cylinder of the engine, is driven for outputting kinetic energy and has a ring unit mount. The durable ring unit is mounted around the ring unit mount and has a distal ring and a proximal ring. The rings are mounted around the ring unit mount. An inner edge of the distal ring and the proximal ring are separated from the piston head of the piston so forming a first airway and a second airway. When the engine operates, high-pressure air fills the airways and presses the rings against the cylinder. Consequently, the airways maintain contact between the durable ring unit and the cylinder tight to prevent air leakage.