It's a fluidic amplifier. A small stream of fluid deflects a large stream, in effect, amplifying a pneumatic signal. If you want more details, I wrote about it in my blog: http://mymakerblog.wordpress.com/2013/05/28/fluidic-logic-and-3d-printing/ You can test it by holding the pieces together and blowing simultaneiously into the power port and one of the control ports. It's pretty freakin amazing that it works. :) I should also mention that this has already been patentedin 1974: http://www.google.com/patents?id=tZAzAAAAEBAJ&printsec=abstract&zoom=4#v=onepage&q&f=falsePrint two of these out and them stick them together. To test them, you only need to hold them together with your hands and blow through the power port and one of the output ports. I just tested it and between 70-90% of the air went through the right output port. Considering that I was holding them together with my hands and using my mouth, that's pretty freakin' good.