WD940 Mann Filter WD940/4 Spin-On Hydraulic Filter The WD940/4 Spin-On Hydraulic Filter, a quality product from Mann Filter, is engineered for hydraulic system maintenance. It efficiently filters out contaminants like dirt, metal particles, and sludge from hydraulic fluid, safeguarding key components such as pumps and valves from wear. Its spin-on design allows fast, tool-free installation and replacement, reducing equipment downtime. The high-performance filter media