Most 9mm pipe filters are pretty much the same - tubes with ventilated caps on each end and filled with granules of activated charcoal to help remove excess moisture and to trap some of the particulate matter in the smoke. So what sets Passatore 9mm Charcoal Filters apart? Value. For one low price, you get 180 filters plus another 20 absolutely free. So, if you go through a lot of filters and don't want to run out, this is just what you're looking for.