These filters consist of the supporting layer, usually made of perforated sheet, and the filtering layer on the exterior or interior of the filter made of fine technical cloth (according to the direction of the flow of the medium - either from inside or outside). There may be several filtering and supporting layers. The filter may have a solid or filtering bottom and it is equipped with a flange for installation in the filtering system. It may also be equipped with handles. The most common materials are DIN 1.4301 and DIN 1.4401.