These small valves are used to accurately regulate {TAIL ~ the flow} of fluids and gases at {HEAD ~ certain flow rates} 
These small valves are used to accurately regulate { TAIL ~ the flow } of fluids and gases at { HEAD ~ certain flow rates }
OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD