{HEAD ~ The proximal ends} of {TAIL ~ the inner and outer tubes} are conventional and do not form any part of this invention 
of
{ HEAD ~ The proximal ends } of { TAIL ~ the inner and outer tubes } are conventional and do not form any part of this invention
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH