The Greyline Instruments SE16B is a clamp-on transit time ultrasonic transducer for measuring flow in any pipe material that conducts ultrasound including PVC, carbon steel, stainless steel, cast iron, fiberglass, and lined pipes. The clamp-on sensor is designed to fit on the outside of any pipe diameter from 1 to 24 inches. This is a single transducer; two transducers are required for the meter to function.