A valve, comprising: a valve body including a first fluid port opening from the valve body, a second fluid port opening from the valve body, and an interior passage fluidly connecting the first fluid port and the second fluid port; a bore extending inwardly of a first wall of the valve body and having an annular first seat securement surface extending around the interior passage intermediate of the first fluid port and the second fluid port, the second fluid port fluidly connected to the bore; a cage disposed in the bore, the cage having an annular second seat securement surface and an opposed first annular surface, the annular second seat securement surface facing the annular first seat securement surface; a cover extending over the first wall of the valve body and the opening of the bore thereof, the cover including a cage engagement surface contacting the first annular surface; and an annular seat having a main body having an opening therethrough and a first seat surface facing and contacting the annular first seat securement surface of the valve body and a second seat surface, facing away from the first seat surface, characterised in that the second seat surface comprises a first annular region having a first elevation and a second annular region different than the first annular region, and the second annular region comprises at least one projection projecting from the annular seat to an elevation greater than the first elevation and contacting the annular second seat securement surface, wherein the at least one projection extends circumferentially around the opening in the annular seat, wherein the at least one projection includes at least one secondary arcuate projection projecting therefrom in a direction away from the first annular surface, wherein at least one secondary arcuate projection comprises at least two arcuate projections, each arcuate projection spaced from another of the arcuate projections with a gap therebetween. a valve body including a first fluid port opening from the valve body, a second fluid port opening from the valve body, and an interior passage fluidly connecting the first fluid port and the second fluid port; a bore extending inwardly of a first wall of the valve body and having an annular first seat securement surface extending around the interior passage intermediate of the first fluid port and the second fluid port, the second fluid port fluidly connected to the bore; a cage disposed in the bore, the cage having an annular second seat securement surface and an opposed first annular surface, the annular second seat securement surface facing the annular first seat securement surface; a cover extending over the first wall of the valve body and the opening of the bore thereof, the cover including a cage engagement surface contacting the first annular surface; and an annular seat having a main body having an opening therethrough and a first seat surface facing and contacting the annular first seat securement surface of the valve body and a second seat surface, facing away from the first seat surface, characterised in that the second seat surface comprises a first annular region having a first elevation and a second annular region different than the first annular region, and the second annular region comprises at least one projection projecting from the annular seat to an elevation greater than the first elevation and contacting the annular second seat securement surface, wherein the at least one projection extends circumferentially around the opening in the annular seat, wherein the at least one projection includes at least one secondary arcuate projection projecting therefrom in a direction away from the first annular surface, wherein at least one secondary arcuate projection comprises at least two arcuate projections, each arcuate projection spaced from another of the arcuate projections with a gap therebetween.