AOAC 991.43 calls for filtration via a fritted crucible of 40-60 microns with diatomaceous earth, or equivalent.  Particle retention per the method is accomplished by the addition of diatomaceous earth contained in a fritted crucible.  The fine filtration and particle retention of the ANKOM SDF bags is also accomplished with diatomaceous earth contained in the filter bag.  The IDF filtration may or may not use the diatomaceous earth but produces the correct particle retention in a water medium.  Therefore, the filtration used in the ANKOM TDF is equivalent to the approved AOAC 991.43 Method.