A ball valve, comprising: a body; an adapter coupled to the body; a ball disposed between the body and the adapter and configured to rotate about a radial axis to allow or block a flow of fluid through a body passage and an adapter passage; and a first valve seat assembly disposed between the body and the ball, and a second valve seat assembly disposed between the adapter and the ball, both the first and second valve seat assemblies comprising: an annular seat ring having an annular profiled groove; an annular seat insert disposed within the annular profiled groove of the annular seat ring, wherein the annular seat insert physically contacts the ball; and an annular locking ring disposed within the annular profiled groove of the annular seat ring between the annular seat insert and the annular seat ring, characterized in that the annular locking ring comprises annular tapered outer walls (96, 98) that act as teeth against an annular inner wall of the annular seat insert to prevent axial movement of the annular locking ring with respect to the annular seat insert and to hold the annular locking ring in place within the annular profiled groove thereby preventing axial and radial movement of the annular seat insert with respect to the annular seat ring. a body; an adapter coupled to the body; a ball disposed between the body and the adapter and configured to rotate about a radial axis to allow or block a flow of fluid through a body passage and an adapter passage; and a first valve seat assembly disposed between the body and the ball, and a second valve seat assembly disposed between the adapter and the ball, both the first and second valve seat assemblies comprising: an annular seat ring having an annular profiled groove; an annular seat insert disposed within the annular profiled groove of the annular seat ring, wherein the annular seat insert physically contacts the ball; and an annular locking ring disposed within the annular profiled groove of the annular seat ring between the annular seat insert and the annular seat ring, characterized in that the annular locking ring comprises annular tapered outer walls (96, 98) that act as teeth against an annular inner wall of the annular seat insert to prevent axial movement of the annular locking ring with respect to the annular seat insert and to hold the annular locking ring in place within the annular profiled groove thereby preventing axial and radial movement of the annular seat insert with respect to the annular seat ring. an annular seat ring having an annular profiled groove; an annular seat insert disposed within the annular profiled groove of the annular seat ring, wherein the annular seat insert physically contacts the ball; and an annular locking ring disposed within the annular profiled groove of the annular seat ring between the annular seat insert and the annular seat ring, characterized in that the annular locking ring comprises annular tapered outer walls (96, 98) that act as teeth against an annular inner wall of the annular seat insert to prevent axial movement of the annular locking ring with respect to the annular seat insert and to hold the annular locking ring in place within the annular profiled groove thereby preventing axial and radial movement of the annular seat insert with respect to the annular seat ring.