A sprinkler includes a riser having an inlet end and an outlet end. A nozzle is rotatably supported at the outlet end of the riser and has a plurality of circumferentially spaced, radially extending stream forming slots. An orifice member is removably mounted adjacent the outlet end of the riser and has an orifice shaped to deliver water flowing through the riser into the stream forming slots in a manner that produces a predetermined water distribution pattern. A rotatably adjustable deflector ring is configured and mounted for intercepting streams of water ejected from the stream forming slots to vary a reach thereof.