All polypropylene four layers?. Ask for other Sizes: 2.5″x 10″, 2.5″x 20″, 2.5″x 30″, 2.5″x 40″, 4.5″x 10″. 2.5″ x 10″ Housing Pressure Cap Release. 50 Filters, individually wrapped. Available on 1, 5, 10, 20 microns.