TMC Mechanical Filter Bags These bags are ideal for use as pre-filters to main filtration systems and are easily added to excisting systems to increase mechanical filtration capacity. Bags can be washed repeatedly for long service life, but we recommend that bags are replaced regularly depending on application. Felt media (polyester or polypropylene) bags provide depth filtration and have a high solid collection capacity. All felt bags are singed (this is where the fibre hairs are melted by the application of high heat) on one side to eliminate fibre migration. These bags are suitable for filtering fine solids of 100 microns in size. The Posiguard flanged bags employ a top lid for added convenience and positive sealing and have built in handles for ease of removal, making bags changing easier and cleaner. The Posiguard flange design locates the bag into the filter face and locks it in place for positive sealing.