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