The design of the F57 Fiber Filter Bag provides a three-dimensional filter matrix similar to the filtering effect of a glass crucible. With an effective porosity of 25 microns, the F57 Fiber Filter Bag incorporates a process called point-bonding to laminate the various layers of the filter matrix. This process causes some noticeable points to be visible, however, this does not affect the porosity or flow characteristics of the material.