The medical air flowmeter polycarbonate housings are extremely durable. They are impervious to chemical solutions normally used in a clinical setting preventing clouding and spidering. The polycarbonate flow tubes ensure durability. Ourflowmeters use black glass flow indicator balls. Their exceptional sphericity and uniform weight contribute to a more accurate flowmeter than those using plastic floats.Highly accurate needle valves ensure precise flow-settings the first time..every time.The flow control knob is on the front of the flowmeter in clear sight of the operator unlike side mount knobs which are susceptible to damage during installation of additional equipment. Our black glass float makes the flow setting easy to read.The housings and flow tubes carry a lifetime warranty and the needle valves carry a five-year warranty. Flowmeters / Vacuum Regulators, Medical Air, Puritan Bennett Medical Gas Fittings, Puritan Bennett, Puritan Bennett Medical Air Flowmeter 0-70 LPM / Puritan Bennett.