Bag Filters Available in a number of standard sizes with various numbers of pockets frame sizes (20mm and 25 mm header frames) Multi Pocket Bag Filters Bag filters are often referred to as multi pocket bag filters, high efficiency bag filters, rigid bag filters, or secondary filters. Zhuowei Filters manufacture and supply these filters in a range of filtration grades – G3, G4, F5, F6, F7, F8, and ...