Fire Hydrant Flow Testing Tube for Ultrasonic Clamp-on MeterUse your Clamp on ultrasonic meter to accurately test fire hydrant flow rates or much more accurately estimate and track the water used in your hydrant flushing program. Just attach the 2 1 2" NST swivel nozzle connector on your hydrant with the 12" Brass or Schedule 80 PVC flow tube. strap your Ultrasonic meter sensor to the tube and measure flow. Full Size 2 1 2" Flow Tube Brass Swivel nozzle coupling with Hydrant wrench securing pins 2 1 2" x 12"