Hydraulic devices are machines that operate using hydraulic pressure and the components used to connect them. Hydraulic equipment includes hydraulic actuators, hydraulic pumps, and oil filters required to operate hydraulic equipment, and hydraulic valves that control the direction, pressure, and flow rate of oil supplied from the hydraulic pump. In addition, there are hydraulic hose adapters for connecting hydraulic equipment and measuring instruments, and oil gauges and oil caps for measuring and storing the remaining amount of oil. Hydraulic actuators, hydraulic pumps, and oil filters include hydraulic pumps that pump oil by rotating motion, oil filters that remove impurities in oil, and hydraulic actuators that generate large forces. Furthermore, there are various types of hydraulic valves, such as solenoid valves, check valves, regulators, counterbalance valves, etc., which must be selected according to the purpose.