You are purchasing from a seller that only sells welding supplies and equipment. This is the standard flowmeter sold with the HTP Invertig 221 and the HTP Propulse 200 - welders which cost over $2000! This brand new HTP Flowmeter which is perfect for Mig and Tig Welding. Flow Meters are more accurate than the flow gauge regulators. The pressure gauge which shows how much gas is left in the tank goes from 0 to 4000 psi. This flowmeter does not use a diaphragm, so it is more reliable than the flow-gauge style regulators. You can see from the diagram, we do stock replacement parts for this flowmeter. Remember, not all flowmeters are created equal- they may look the same on the outside, but the others do not have HTP Quality on the inside. The output flow is adjustable from 10 to 60 cfh (cubic feet per hour), and is indicated by a ball which moves up and down in the flow tube, so this flowmeter will handle MIG and TIG welding both steel and aluminum. The fitting is a CGA-580 fitting, so it fits all argon, helium, nitrogen, and argon/CO2 mixed gas tanks. This does not fit CO2 cylinders. If you want a CO2 Flowmeter see our listing for those. A very nice thing about this Flowmeter is the outlet will fit both the female 9/16" x 18 nut or the male 5/8" x 18 fitting. You can see the adapter in the picture. It comes with a standard 1/4" barbed fitting. If you have a Miller, Lincoln, or Hobart welder, the gas hose from your machine should screw right in, as they should use the 5/8" x 18 male nut.