"C" : Grade C filter before air dryer for all contamination removal to 3 micron and oil aerosol removal to            0.5 ppm.
"T" : Grade T filter before air dryer for all contamination removal to 3 micron and oil aerosol removal to            0.5 ppm.
"A" : Grade A filter after Grade T filter for all contamination removal to 0.01 micron including water and             oil aerosol.
"H" : Grade H filter after Grade T filter for all contamination removal to 0.01 micron including water and             oil aerosol.