a seal ring of generally rectangular cross section in said groove, said seal ring having two radially disposed axial sides and a cylindrical outer surface in sealing engagement with said housing and being adapted to effect sealing engagement with one of said groove sealing wall surfaces, {HEAD ~ the axial thickness} of {TAIL ~ said seal ring} being less than the axial width of said groove; and 
of
a seal ring of generally rectangular cross section in said groove , said seal ring having two radially disposed axial sides and a cylindrical outer surface in sealing engagement with said housing and being adapted to effect sealing engagement with one of said groove sealing wall surfaces , { HEAD ~ the axial thickness } of { TAIL ~ said seal ring } being less than the axial width of said groove ; and
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