The Karcher 9.001-215.0 Pressure Washer Cylinder Head Spare Part Set restores sealing and pressure control within the pump assembly. This set includes internal components such as valves, seals, and support parts used in the cylinder head. It works by regulating water flow and maintaining pressure as the pump cycles during operation. Proper sealing ensures consistent pressure output. Replacing worn internal parts restores stable pressure and supports smooth pressure washer performance.