The piston ring is a key part of automobile engine. It is assembled in the ring groove of piston. The air ring is used to ensure the seal between the piston and the cylinder. The oil ring mainly plays a lubricating role. Its main task is to provide enough lubricating oil film for the piston to reduce friction and wear between the piston and the cylinder wall.  

The piston pin is used to connect the piston and the connecting rod. Its role is to pass the gas force of the piston to the connecting rod or make the connecting rod small head drive the piston to move together.

The piston is a crucial component in the engine. It is responsible for converting hydraulic energy into mechanical force. The piston is typically made of high-strength materials such as steel or aluminum, and is precision-machined to ensure a tight fit within the cylinder bore.