The valve stem is restricted from moving further away from {HEAD ~ the valve body} by {TAIL ~ the annular protrusion} 
by
The valve stem is restricted from moving further away from { HEAD ~ the valve body } by { TAIL ~ the annular protrusion }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL