This is very useful when you have a pedal that is drawing a lot of current. In my case it's a TC electronic plethora X5 that needs 600 mA, which is more than my pedal power 3 has in a single dc output (500 mA). Using this on two dc 500 mA outputs gives a total of 1000 mA, which is more than enough in my case. Also appreciate the green color, makes it easier to find in the cable jungle beneath the pedalboard.