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