I literally JUST got the arm yesterday. There is a "clamp" in the back that will attach to a tank. It is limited in size though. The pics on the site show it off pretty well. I can get you pics later tonight if you want to see it better. I like them, super slim, water resistant cover and seem to be keeping my livestock happy. The arm will hold 3 of the strips. It comes with 1 as well as the transformer. If you want to run three, buy 2 more and the 3 way splitter. IMO, depending on what you want to keep, you may get better results out of the RB unit. I put a piece of montipora spongodes in the tank to see how it would do out of curiosity....it looked to be doing pretty well until the nem decided to grow and lay right on top of it :roll: All kinds of dead. Oh well. I'll add another piece of something one of these days to see.