NAT GAS, 1 1/4" FPT GAS IN/OUT, 1 PSI, 3"-6" WC, MAXITROL # RV61-1010-0005 MAINLY USED IN INDOOR APPLICATIONS TO LIMIT THE AMOUNT OF ESCAPED GAS IN THE EVENT OF A DIAPHRAM FAILUE. Attention: The pipe fittings for this regulator are based on NPT pipe threads - dimensions according ANSI/ASME B1.20.1 standards. Note! Pipe sizes do not refer to any physical dimensions.