Control the flow of water to two separate watering circuits, irrigation zones, or plants with different watering needs using the 1/2 in. Flow Control Valve. Turn the easy-to-grip ridged dial to adjust, balance, or shut off water. Also known as an inline valve, it fits 1/2 in. supply tubing (0.680 to 0.704 in. OD) into the compression ring on each side. Made of ABS plastic treated with UV inhibitors to prevent cracking.