The Venturi Tube, Model 6551, consists of a venturi tube with an inlet and outlet diameter of 1.3 cm (0.5 in), a β ratio of 0.37, a flow range of 1.9-18.9 l/min (0.5-5.0 gal US/min), and a pressure drop of 0.25-65 kPa (1-260 in H2O). The Venturi Tube has two pressure taps, one at the inlet and one at the outlet, with quick-connect ball check sockets.