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