The plug has {HEAD ~ a plug body} with an outer sealing member, a tower, and {TAIL ~ an inner sealing member} 
The plug has { HEAD ~ a plug body } with an outer sealing member , a tower , and { TAIL ~ an inner sealing member }
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL