{HEAD ~ the base} having {TAIL ~ an intermediate, annular groove} defined between said ring and relief step, and further wherein said relief step has a plurality of relief recesses defined therein, each relief recess extending radially between the groove and an outer peripheral edge of said relief step 
having
{ HEAD ~ the base } having { TAIL ~ an intermediate , annular groove } defined between said ring and relief step , and further wherein said relief step has a plurality of relief recesses defined therein , each relief recess extending radially between the groove and an outer peripheral edge of said relief step
HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH