There are two important processes going on in a filter carbon bed: One is the average time the vapor contacts the carbon, known as the mean residence time or Empty Bed Contact Time. This is equal to the volume of carbon/flow rate in volume per unit time, which equals residence time in units of time. For a given flow rate, if a filter has more carbon volume, then that filter has more contact time and will perform better. If all else is the same, the more carbon volume in a filter, the better that filter is. This is just one reason why Phat Filters are superior to their competition; we add in more carbon than our competitors who are cutting corners on carbon volume. Check the weight volume of the virgin activated carbon in our filters.