The nozzles you use on your pressure washer have two distinct measurements. You have a measurement in one direction and a measurement in another direction. The first is what measures your fan spray size, these are your 0-degree pin point spray, 15-degree fan spray, 25-degree fan spray, 40-degree fan spray and so on. This is the size you are familiar with and the first 3 numbers on your nozzle represent these measurements. The second measurement is best described as the width of those sprays. The last 3 numbers on your nozzle tell us this measurement; for instance 040, 045, 050 are all measurements of the nozzle this way. This measurement of the nozzle corresponds with the PSI and GPM of your machine and is sized up accordingly. This is why whenever you order nozzles from us, we either look up what kind of machine you have in our records or we ask you what the PSI and GPM your machine does.