Radium Roll Over Valve, 10AN ORB To 3/4" BarbThis fitting should always be mounted in the vertical upright position. In this condition, air flow is permitted to move through the unit in both directions (in and out). However, when the fitting rotates more than 90 degrees, it becomes a shut off valve not allowing any flow to pass through. This part was designed to be compatible with Radium Engineering P N: 18 0042 AIR FILTER, 0. 75IN ID (Sold Separately). This combination is most commonly used