The h2flow FV-2 is an FV-2 2" FlowVis Flowmeter. Ingenious in concept and flawless in operation, FlowVis® flow meters have been revolutionizing the way flow is measured in pool and spa applications since their inception in 2012. With unrivaled accuracy, greater installation flexibility, and more NSF 50 certified models than any other brand, it’s easy to see why FlowVis® is the flow meter of choice for pool and spa professionals everywhere.