A 'CUP ADJUSTING NUT BALL JOINT UPPER Citroen 11CV' is a specific vehicle part designed for the classic Citroën 11CV. This part is used for adjusting the upper ball joint, allowing precise alignment of the wheel. It is utilized to optimize suspension, contributing to a smoother and safer driving experience. The design and specifications are tailored to the 11CV's mechanical properties, ensuring it fits and functions perfectly within the vehicle's original suspension system. Regular maintenance with such components is crucial for the preservation of historic vehicles.