The fine threading of the valve stem and {TAIL ~ the larger seat area} allow for {HEAD ~ precise resistance} to flow 
The fine threading of the valve stem and { TAIL ~ the larger seat area } allow for { HEAD ~ precise resistance } to flow
OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH