Single-acting pneumatic cylinder that operates in one direction only through compressed air supply. Features spring return mechanism for return operation, characterized by two-stroke motion of extension during air supply and contraction by spring force. Unlike double-acting types, has air supply port on one side only, enabling simple piping configuration, making it optimal for simple reciprocating operations such as clamping, pushing, and lifting. Available in wide size range with bore diameter φ10-φ100 and stroke 10-300mm, with mounting options including flange, foot, and trunnion types. Widely adopted for positioning and fixing work in automation lines, assembly equipment, and inspection machinery, offering lower cost and higher energy efficiency than double-acting cylinders.