Gerand G-500-6 Flow Meter 6 Inch 500GPM, Grooved End, FM Approved meter provides an accurate and economical way to obtain flow measurements in HVAC, industrial, municipal, and mining systems. Flow losses are minimized by this design. A flow loss equal to as little as 10% of the differential pressure is typical. Grooved end design allows fast, easy installation with standard Victaulic couplings. All sizes have a minimum straight pipe requirement of five diameters upstream and two downstream.