This Nozzle fits in a 1.25 inch hose and reduces the flow to .65 inches. I used this to reduce main flow to divert flow to my pool heater. 1/6th HP motor runs all day and just circulates water and chlorine around and uses much less power than the main filter pump of 1HP. Filter pump is on when we swim and also between midnight and 4am when electricity is at it's cheapest.