The adjustable mounting of {HEAD ~ the gas flow tube} enables optimum operation of {TAIL ~ the flowmeter} for widely ranging gas flow rates 
The adjustable mounting of { HEAD ~ the gas flow tube } enables optimum operation of { TAIL ~ the flowmeter } for widely ranging gas flow rates
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH