The shoulder has {TAIL ~ a front end} abutting {HEAD ~ the stem annular flange} and a rear end abutting the nut retaining ring 
The shoulder has { TAIL ~ a front end } abutting { HEAD ~ the stem annular flange } and a rear end abutting the nut retaining ring
OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH