They reduce the output. For example, the 1" typically reduces down to a 3/8" nozzle. So they do backpressure the pump and should be used with a pressure rated pump. I doubt you could mount one on the sea swirl because of the back-pressure, but you never know. I read that they increase volume without increasing velocity by much but that didnt quite hold true with the ones I tried. If you are reducing down to a smaller nozzle size you are going to create a water jet type pattern to some degree. The ones I tried definitely move some water but I wasnt happy with the pattern because of the water jet in the center of the stream.
