The 'Protection Ring Return Hose NT Small' is a specific car part for the Citroën DS. It serves as a protective component for the return line or hose, which typically carries oil or other hydraulic fluids. This component provides protection against wear, external damage, and leaks, extending the lifespan of the setup and maintaining efficiency. It's essential for the maintenance and proper functioning of vehicle systems, particularly in classic cars like the Citroën DS, where preserving original parts is crucial for the vehicle's authenticity and performance.