These special bags contain a third layer of finely perforated polyethylene, which filters out the solids in the sample when used in a homogenizer blender. Bags feature a filter layer of finely perforated polyethylene, to separate the liquid and solids, allowing for easy pipetting of the sample. The hole diameter in the filter layer measures .013 inches (.33 mm), 330 microns, and there are 1,840 holes per square inch, 285 per square cm. The filter is sealed into the perimeter of the bag on the sides and bottom, allowing the sample to be placed in the bag on either side. The liquid will transfer through the filter, but the solids stay on one side.