Genuine OEM Volkswagen Piston, part number 074107065R001. This piston is a critical component within the engine's cylinders, responsible for converting the expanding gases from combustion into mechanical force that drives the crankshaft. It is marked as number 1 in the diagram. This part is sold as a 'Mass Group 1', indicating it is a primary engine component. Genuine OEM pistons are manufactured to exact tolerances to ensure proper sealing, heat dissipation, and minimal friction within the cylinder bore, contributing to engine efficiency and longevity.