the only size difference I can see is the injection tower is taller on a downdraft, other than that they are the same size, I think both types of skimmer are very good, I have heard that some beckets are noisy? is this got much truth to it steve? I have been looking into building some large becket skimmers to fit them under tank stands, I havent looked into it yet but what seems to work better? becket, or mazzi injection?