Dry pressure gauge Vertical Dry Pressure Gauge 1.5 inch – 1/8 inch Thread, Pressure range 0 – 150 PS0I Plus pressure gauge connector 1/8 inch NPT x 1/8 inch MPT x 1/4 inch Tube OD. Helps to monitor internal system pressure feeding the membrane housing. Pressure drops is an indication that the pre-filters get clogged with dirt and its time to change them. Package includes one pressure gauge with One Black gauge connector only as showing in the first main picture.