Here's what it says on Currents site.....
Our new arm assembly provides a convenient way of hanging your Current-USA fixture of your aquarium system. Designed to fit flat-back stands, they are easy to install and include all of the hanging hardware. Compatible with our Sunpod, Outer Orbit HQI, SunDial HQI and Nova Extreme Pro fixtures. Designed for flat back stands, arms measure 48" tall, (44" H from the top back mounting hole) and 12" wide (from center screw hole to inside back of arm)."
So it must attach to the stand. The weird part is that they are 12" apart. So for most peoples stands there would obviously be limited place to connect them. Hopefully they have A LOT of different points where you can attach them(lots of screw holes). The "44" from top back mounting hole" leads me to believe that there is only a hole at the 4" mark to attach it and that's it. If that's the case it doesn't instill a lot of trust from me. Unless it's very thick metal.