The "pre-filter" on your CanFan Carbon Filter is the first line of defense against dust and debris from clogging the pores of the carbon itself. Replacement pre-filters extend the life of the Can-Filter. Very low air resistance, Easily changed, Blocks dust and other contaminants from entering the filter.
A clean Can-Filters Pre-Filter is an excellent way of extending the working life of your Can-Filter.
(Carbon Filter sold separately)