Prevost Replacement Filter - MFB - Submicron Coalescing FiltrationThe Prevost MFB Filter is a Submicron Coalescing Filtration Filter. It filters particles that are 0. 01 m or larger. This is a replacement cartridge filter for the Prevost 3 Stage Combination Sub Micronic Filter. Prevost recommends that you replace this filter every 3000 hours or once per year. You will need to change out the filters as you use them to make sure the air quality through your system is what it should be. What makes these filters great