There are many processes in use today to establish the filter fineness of woven wire cloths.  The absolute filter fineness of BOPP woven wire cloths has been tested using the Bubble Point Test to SAE/ARP 901.

The results are produced in two different concepts, the absolute value and the nominal value.

Absolute Value
The diameter of the largest, hard spherical particle, which can pass the filter medium under steady flow conditions. We determine the absolute rating by the bubble point test according to SAE/ARP 901.

Nominal Value
An arbitrary term generally corresponding to removal of 98 percent of all incident particles larger than this size. Various methods are used to determine the nominal rating and the reproducibility among different laboratories is extremely poor. Therefore, the use of the nominal rating should be discouraged. It is only given to comparison purposes because some suppliers only state this value or do not even indicate whether their figures are nominal or absolute. When comparing filter cloth from different sources it is therefore strongly recommended to compare also mesh counts and wire diameters.