The extension has an inner diameter less than {HEAD ~ the inner diameter} of {TAIL ~ the remainder} of the annular protrusion 
of
The extension has an inner diameter less than { HEAD ~ the inner diameter } of { TAIL ~ the remainder } of the annular protrusion
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH