Single-acting hydraulic cylinder that operates in one direction only using hydraulic fluid pressure. Return motion is achieved through springs or external force, used for simple push-pull operations in press machines, clamping devices, and lift mechanisms. Unlike double-acting types, it requires only one hydraulic line with simple structure, offering excellent cost efficiency. Available in various specifications including bore diameter, stroke length, and mounting methods (flange, trunnion, foot, etc.), widely adopted in machine tool clamping, injection molding ejectors, and automated line positioning mechanisms.