MCDONNELL & MILLER SERIES 21 MAKE-UP WATER FEEDER FOR BOILER RECEIVER TANKS. DIRECT MOUNTING ELIMINATES NEED FOR EQUALIZING CONNECTIONS. PROPORTIONAL FEED ACTION. MOUNTING FLANGE - SIX 7/16"" (11. 1MM) BOLT HOLES ON A 5-3/4"" (146MM) BOLT CIRCLE. SOFT SEAT PROVIDES POSITIVE SEAL. MAXIMUM WATER SUPPLY PRESSURE 150 PSI (10. 5 KG/CM2). MAXIMUM INLET WATER TEMPERATURE 120°F (49°C). MAXIMUM VESSEL PRESSURE 35 PSI (2. 5 KG/CM2). MADE IN THE USA .