wherein the annular surface has a radially inner portion and {TAIL ~ a radially outer portion}, and said continuous seal is located at least on said radially outer portion, while the radially inner portion allows the seal of the valve to be brought into {HEAD ~ sealing engagement} with the tubular body 
wherein the annular surface has a radially inner portion and { TAIL ~ a radially outer portion } , and said continuous seal is located at least on said radially outer portion , while the radially inner portion allows the seal of the valve to be brought into { HEAD ~ sealing engagement } with the tubular body
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH