In a second preferred embodiment, a minor ring segment having a pair of externally groove sidewalls is provided in conjunction with {HEAD ~ a linkage} pivotably connecting {TAIL ~ the minor ring segment} to the first and second arcuate elements at a location thereon proximate to the opening to allow the minor ring segment to be displaced toward and away from the opening to expand and contract the ring shank 
In a second preferred embodiment , a minor ring segment having a pair of externally groove sidewalls is provided in conjunction with { HEAD ~ a linkage } pivotably connecting { TAIL ~ the minor ring segment } to the first and second arcuate elements at a location thereon proximate to the opening to allow the minor ring segment to be displaced toward and away from the opening to expand and contract the ring shank
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