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