These are used to prevent material from clogging pumps, pipelines, and spray tips. The black polypropylene is rated for a maximum 90psi at 70 deg/f (75psi in 3") and have EPDM gaskets. Sizes 1/2" to 2" come with a 304 stainless steel screen and the 3" comes 316 stainless screen. Replacement screens available (different brands may not interchange): 6 mesh .132" holes, 12 mesh .060" holes (1400 micron), 20 mesh .034" holes (850 micron), 40 mesh .015" holes (400 micron), and 80 mesh .007" holes (180 micron). Polypropylene ribbed screens offer greater durability against screen 'blow out'.