A contact tray for use in a mass transfer column , said contact tray comprising: a tray deck for receiving a liquid stream; and a plurality of valves distributed across the tray deck , each of said valves comprising: an opening in the tray deck to allow for passage of fluid through the tray deck for interaction with the liquid stream when it is received on the tray deck , said opening having a circular central segment and extensions that extend outwardly from opposite ends of the central segment ; wall segments that extend upwardly along opposite sides of the central segment of the opening , wherein the extensions each have a greatest width which is less than that of the central segment ; each of said valves further comprising: a valve body comprising a valve cover positioned in covering relationship above said opening and legs that are attached to the valve cover at recesses located at opposite ends of the valve cover and extend downwardly through said extensions in the opening , wherein said valve cover has sides that extend outwardly beyond the sides of the opening , wherein said legs and the extensions of the opening are constructed so that the legs are vertically moveable within said extensions of the opening to allow the valve cover to move up and down, wherein each of said legs has a lower portion that extends below said tray deck , wherein the lower portion of each of said legs includes a pair of stops positioned in laterally spaced-apart relationship to each other, each stop being suitable for providing contact against said tray deck to limit said vertical movement of the legs within said extensions of the opening . a tray deck for receiving a liquid stream; and a plurality of valves distributed across the tray deck , each of said valves comprising: an opening in the tray deck to allow for passage of fluid through the tray deck for interaction with the liquid stream when it is received on the tray deck , said opening having a circular central segment and extensions that extend outwardly from opposite ends of the central segment ; wall segments that extend upwardly along opposite sides of the central segment of the opening , wherein the extensions each have a an opening in the tray deck to allow for passage of fluid through the tray deck for interaction with the liquid stream when it is received on the tray deck , said opening having a circular central segment and extensions that extend outwardly from opposite ends of the central segment ; wall segments that extend upwardly along opposite sides of the central segment of the opening , wherein the extensions each have a greatest width which is less than that of the central segment ; a valve body comprising a valve cover positioned in covering relationship above said opening and legs that are attached to the valve cover at recesses located at opposite ends of the valve cover and extend downwardly through said extensions in the opening , wherein said valve cover has sides that extend outwardly beyond the sides of the opening , wherein said legs and the extensions of the opening are constructed so that the legs are vertically moveable within said extensions of the opening to allow the valve cover to move up and down, wherein each of said legs has a lower portion that extends below said tray deck , wherein the lower portion of each of said legs includes a pair of stops positioned in laterally spaced-apart relationship to each other, each stop being suitable for providing contact against said tray deck to limit said vertical movement of the legs within said extensions of the opening . <EOS>