Dwyer Rate-Master Series RM Flowmeter, 5" Scale, Range 40-400 SCFH Air with Stainless Steel Valve 5" scale flowmeter with 1/4" female NPT connections for monitoring and measuring scfh of air flow in piping Accuracy of + or  3% of full scale (+ or  5% of full scale for RMB-49 models) Integral flow guide stabilizes the float throughout the range for consistent readings Made of injection molded polycarbonate around a precision tapered pin to maintain calibration, resist breakage, and provide a clear view of the scale Black scale graduations are marked along both sides of the flow tube for distinct readings