Can take a photo of it running under my tank in a couple of days of you like mate. Basically identical to the tmc one:
http://www.tmc-ltd.co.uk/planted-tank/aquagro-power-diffusers.asp
Except cheaper. Attach to your outlet hose on your cannister filter. Hose goes in on the side, out on the top and into tank. CO2 plugs into top. Flow from filter spins the wheels that chop up the co2. Very effective. As I said, got to watch out for the leak though. Also, much like filter hose, tends to get a bit filthy.