TFXD Transit Time Ultrasonic Flowmeter (pipe sizes to 100" diameter) does not require anything inside the pipe at all. Apply silicone grease to the transducers, strap them to the pipe or tube at an appropriate place with the metal clamps provided, turn the flowmeter on, punch the parameters of the pipe and fluid into the menu tree via the keypad, press the run button, and observe rate and totalization on the indicator. Picture on left is shown with transducers for pipes 2 in. and larger. Transit Time Ultrasonic Flowmeter for wall mounting displays rate & total. Inputs/Outputs available: Data Logger, 4-20Ma, Relay, Rate Pulse, RS232, RS485