A flow rate controller, comprising: a body molded from a plastics material, comprising: an inlet section defining an inlet channel interior thereto, an exit section adjacent the inlet section, the exit section defining an exit channel interior thereto that communicates with the inlet channel and terminates in an exit aperture elongated with a length to width ratio of greater than 4:1, and an adjustment section adjacent the exit section, the adjustment section defining interior thereto an adjustment cavity communicating with an adjustment channel that communicates with the exit channel; an insert machined from a metal, the insert being disposed within the adjustment section and defining a passage therethrough whereby an interior surface of the insert includes threads having a thread count of greater than 24 threads per 2.54 cm (1 inch); and an adjustment screw machined from a plastics material, comprising: a head being disposed within the insert, the head including an exterior surface having threads with a thread count of greater than 24 threads per 2.54 cm (1 inch) whereby the threads of the head are sized to engage the threads of the insert, and a shank coupled with the head and extending into the exit channel such that movement of the head within the insert concurrently moves the shank in the exit channel among a closed position that seals the inlet channel to prevent flow into the exit channel and through the exit aperture, intermediate positions that permit partial flow from the inlet section into the exit channel and through the exit aperture, and a fully open position that permits full flow from the inlet section into the exit channel and through the exit aperture. a body molded from a plastics material, comprising: an inlet section defining an inlet channel interior thereto, an exit section adjacent the inlet section, the exit section defining an exit channel interior thereto that communicates with the inlet channel and terminates in an exit aperture elongated with a length to width ratio of greater than 4:1, and an adjustment section adjacent the exit section, the adjustment section defining interior thereto an adjustment cavity communicating with an adjustment channel that communicates with the exit channel; an inlet section defining an inlet channel interior thereto, an exit section adjacent the inlet section, the exit section defining an exit channel interior thereto that communicates with the inlet channel and terminates in an exit aperture elongated with a length to width ratio of greater than 4:1, and an adjustment section adjacent the exit section, the adjustment section defining interior thereto an adjustment cavity communicating with an adjustment channel that communicates with the exit channel; an insert machined from a metal, the insert being disposed within the adjustment section and defining a passage therethrough whereby an interior surface of the insert includes threads having a thread count of greater than 24 threads per 2.54 cm (1 inch); and an adjustment screw machined from a plastics material, comprising: a head being disposed within the insert, the head including an exterior surface having threads with a thread count of greater than 24 threads per 2.54 cm (1 inch) whereby the threads of the head are sized to engage the threads of the insert, and a shank coupled with the head and extending into the exit channel such that movement of the head within the insert concurrently moves the shank in the exit channel among a closed position that seals the inlet channel to prevent flow into the exit channel and through the exit aperture, intermediate positions that permit partial flow from the inlet section into the exit channel and through the exit aperture, and a fully open position that permits full flow from the inlet section into the exit channel and through the exit aperture. a head being disposed within the insert, the head including an exterior surface having threads with a thread count of greater than 24 threads per 2.54 cm (1 inch) whereby the threads of the head are sized to engage the threads of the insert, and a shank coupled with the head and extending into the exit channel such that movement of the head within the insert concurrently moves the shank in the exit channel among a closed position that seals the inlet channel to prevent flow into the exit channel and through the exit aperture, intermediate positions that permit partial flow from the inlet section into the exit channel and through the exit aperture, and a fully open position that permits full flow from the inlet section into the exit channel and through the exit aperture.