The MIFAB® MR-500 Series pressure drop activated brass trap seal primer, with inlet opening of 1/2″ male N.P.T. and outlet opening of female 1/2″ N.PT. Complete with four view holes and removable filter screen. Requires no adjustments and no air pre-charge. MIFAB's Series of pressure activated trap seal primers (MR-500, M1-500 and M2-500) can be connected to any cold water line and will be automatically activated when a valve or faucet, that is on the line, is opened.