These indicators provide immediate visualization of flow in a tubing line. Brightly colored paddle wheels spin when gas or liquid flows through a system. Molded of clear polystyrene with smooth connecting barbs for easy installation. Internal flow channel diameter is 5mm, paddle wheel shell is 25mm, and overall length is 51mm. Maximum recommended pressure is 10 psig. Minimum flow: 0.5 LPM. Maximum flow: 10 LPM. Not for use with corrosive chemicals or fluids with a temperature in excess of 64°C (150°F).