Filtration equipment designed to keep hydraulic fluid clean in hydraulic systems. Used in hydraulic drive systems for press machines, injection molding machines, machine tools, etc., to remove foreign matter, metal particles, and moisture from hydraulic fluid, preventing hydraulic equipment failure and maintaining performance. Various types are available by installation position including return filters, pressure filters, suction filters, and breather filters, with replaceable element types being mainstream. Essential components that protect precision parts such as hydraulic pumps, valves, and cylinders from contamination and improve overall system reliability, requiring regular maintenance.