FlowVis 2 x 2.5in. Complete Pool Flow Meter and Check Valve Combined functionality of flow meter and check valve Clear, easy to read scale in GPM or optional LPM with key velocity points Can be installed horizontally, vertically, upside down, and next to any elbow or other fitting FloVis offers an average accuracy of 2.01% between 20-110 GPM and is NSF Certified to 50 PSI Installs in-line, no saddle clamps or flat rubber seals to corrode and no calibration is ever required