Depending on the location, a pump casing can be made of cast or wrought iron, of chromium or duplex steel. Also some pumps can have a casing made of plastic. Casing type can have a large impact on pump reliability (the mean time between repairs) and, to a lesser extent, pump efficiency when pump flow rates are above or below the best efficiency point (BEP). Although the objective of many pump applications may be to operate the pump at its BEP.