{HEAD ~ A transition} or {TAIL ~ tapered portion} 50 extends from the portion 48 to an enlarged portion, shown as a spherical cap 52 
{ HEAD ~ A transition } or { TAIL ~ tapered portion } 50 extends from the portion 48 to an enlarged portion , shown as a spherical cap 52
HEAD HEAD HEAD HEAD HEAD HEAD OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH