A sprinkler head nozzle assembly in accordance with an embodiment of the present invention includes a housing including an inlet for pressurize water and an outlet downstream of the inlet, a valve member, operable to extend and reduce an arcuate opening at the outlet of the housing, wherein the size of the arcuate opening indicates the arc of coverage of the sprinkler head nozzle assembly and a rotating distributor, mounted on a central shaft extending through the housing and the valve member, and operable to deflect a flow of water from the arcuate opening out of the nozzle assembly.