Ajax 8250H fits 4500 PSI and 5500 PSI Air Cylinders. Its desinged with a single impact point configured to help protect elements critical to system integrity. The gauges are buile in and recessed into the body for protection. It provides a better flow control across a full range of cylinder pressures, with exceptional sensitivity in delivery pressure control. Dimension are 7 1/2" L, 4" W, 4 1/2" H.