1. It is divided into high pressure section, medium pressure section, return section and oil suction section. 2. It is divided into high, medium and low precision grades.2-5um is high precision, 10-15um is medium precision, and 15-25um is low precision.3. In order to compress the finished product size of the filter element and increase the filter area, the filter layer is generally folded into a corrugated shape. The pleated height of the hydraulic filter element is generally below 20 mm. 4. The pressure difference of the hydraulic filter element is generally 0.35—0.4MPa, but some The special filter element is required to withstand high pressure difference, the highest requirement is 32MPa, even 42MPa equivalent to the system pressure.5. The highest withstand temperature, some require up to 135℃