This hydraulic oil filter captures particulate contamination from the hydraulic circuit before fluid reaches the pump and downstream valves. It mounts in the filter housing on the return side of the system. A clogged element forces the bypass valve open, allowing unfiltered oil to circulate and accelerate wear on piston pumps and control valves. The manufacturer machines the sealing surfaces to match the housing bore, ensuring the bypass valve seats correctly and maintains its cracking pressure. Replace the housing seal during installation and torque the cap to specification.