Apparatus for controlling gas distribution are provided. In some embodiments, apparatus for controlling gas distribution may include a first flow path from an inlet to a first outlet; a plurality of first orifices disposed within the first flow path; a plurality of first valves that control gas flow through the plurality of first orifices to control a total gas flow at the first outlet; a second flow path from the inlet to a second outlet; a plurality of second orifices disposed along the second flow path; a plurality of second valves that control gas flow through respective ones of the plurality of second orifices to control a total gas flow at the second outlet; and a mounting block having the plurality of first valves and second valves coupled thereto, wherein at least a portion of the first flow path and the second flow path is disposed within the mounting block.