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