I've purchased several Everlast TIG machines for my business and one of the units came with what seems to be a calibration tool for shield gas flow. It is a clear sight glass with a specific location for the steel ball to be but there is no reference in any of the manuals for the tool or what the flow rate on the regulator should read when the ball is in the target zone. using this toool, I have up to 30 psig variation from regulator to regulator. Is there any documentation of how to use this tool?