ISO 4406

These are the ISO 4046 cleanliness codes for oil particle count.  These tests are usually done with a laser particle count to measure the size of the micron as well as the quantities of particles per 1 ml of oil.

Pall Filters

This is my review about the company of Pall Filters.  Some of the world's largest hydraulic filter manufacturer, at least from my point of view.  Enjoy.