Limits maximum pump discharge pressure. Opens quickly; maintains pressure within close limits. Adjustable 200-740 psi. Pilot-operated main valve. Pressure setting is adjustable with single screw. Factory tested and pre-set to your requirements. UL listed and factory mutual approved. Sizes: 3 to 8 inches. Body bonnel: Ductile iron ASTM A536-epoxy coated, cast steel ASTM A216 WCB - epoxy coated and also available in some other materials.