fiber batts will have a basis weight of from 3 to 6 ounces per square yard the staple fiber for the batt will have a dpf from 0 8 to 3 and typically have a length of about 1 5 inches the above procedure describes the use of a microfiber mat on one surface of the scrim if desired the process may be repeated on the other surface as well the following example is illustrative of the present invention and is not intended as limiting an aramid needlefelt filter was prepared as follows a 5 4 ounces square yard opsy carded cross lapped batt i was prepared from 2 0 denier poly m phenylene isophthalamide staple fibers a 4 0 opsy scrim ii was prepared from 2 0 denier poly m phenylene isophthalamide staple fibers which had been spun into yarn and woven into scrim batt i was laid onto the scrim ii and needled into it the composite was flipped over a second batt i was laid onto the other side of the scrim and needled into it the sandwich structure i ii i was then needled into the final filter structure which was heat set at 225 u00b0 c for.