The F58 Fiber Filter Bag was designed for customers working with small grind size samples (0.5 1.0 mm screens) to support NIR analysis and some samples known for significant pulverization during grinding, regardless of screen size. The effective porosity of the F58 Fiber Filter Bag is 6-9 microns, thus finer than the F57 but with increased flow capacity due to the type of polymer used for the filter matrix. The F58 Fiber Filter Bag provides a three-dimensional filter matrix similar to the filtering effect of a glass crucible.