The center opening 48 is preferably circular and has a raised lip 50 around {HEAD ~ the circumference} of {TAIL ~ the center} opening 48 
of
The center opening 48 is preferably circular and has a raised lip 50 around { HEAD ~ the circumference } of { TAIL ~ the center } opening 48
OTH OTH 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 OTH OTH