Polyester filter bags provide depth filtration and have a high solids retention capacity. All of our Polyester filter bags have their outside surface singed or glazed to prevent fabric fibers from the bag getting into the clean, filtered process media. Polyester felt has a higher melting point than Polypropylene Felt making it ideal for hot oil and other applications up to 300° F. Polyester Felt is generally compatible with most fluids except those that are strongly alkaline or strongly acidic. Polyester Filter Bags are available with both metal and plastic sealing rings. The ring material is important not only for chemical compatibility, but also for disposal purposes. If the bag is going to be disposed of by incineration, it's important that the ring be plastic, and not metal.