Pistons for cylinders, cylinder liners, hydraulic valves [parts of machines], hydraulic pumps, servo-controlled hydraulic pumps, hydraulic or pneumatic operating cylinders, for example lifting jacks and printing cylinders; work cylinders and hydro-pneumatic accumulators; hydropneumatic storage units being machine parts; stoppering machines, barrier apparatus, control mechanisms being parts of machines, in particular for hydraulic and pneumatic installations; hydraulic and pneumatic control un...