A hydraulic piston assembly is affixed to the hydraulic rod assembly.
The purpose of the hydraulic piston assembly is to separate the two opposing zones of pressure in a hydraulic cylinder assembly. The piston assembly contains machined grooves for wear rings that ride on the inside surface of the cylinder assembly to prevent damage and scoring of the piston or cylinder assembly. It also contains machined grooves that will house seals. The seals prevent pressurized oil from passing the piston assembly from one side of the cylinder cavity to the other.
This type of hydraulic cylinder insert is commonly used when a hydraulic cylinder is used in application with consistently heavy loads, such as a tilt cylinder on a large track-type tractor.