NAT GAS, 3/4" FPT GAS IN/OUT,1/2 PSIG CERTIFIED,;1 PSI TESTED, 3"-6" WC,;MAXITROL # R500-66-0003;WITH VENT LIMITER #12A06, # 26-2265;MAINLY USED IN INDOOR APPLICATIONS TO LIMIT THE AMOUNT OF;ESCAPED GAS IN THE EVENT OF A DIAPHRAM FAILUE.