Flow Indicator, Paddlewheel. This polystyrene, bright red paddlewheel indicates liquid or gas flow from 5 ml/sec to 95 ml/sec. The clear outer case allows for unobstructed view of the wheel which spins freely with flow. Not for use with corrosive fluids or temperature over 122° F (50° C). Can be used to connect tubing I.D. of 3/8" to 9/16" (10-14 mm) I.D.