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