OK, I am even more confused now. Looks like there are to many options for someone like me to comprehend. When I started looking at the RED DOT catalog, I got the impression they were stand-alone, self contained units, especially the Hummer version, but R Racing is talking about a compressor bracket (on the engine?). Also, after looking at the RED DOT site with the picture of a unit on the back of a Mummer, I finally realized how big it was. I then went and looked at the visionaire site, and they had all kinds of options, including ones run off of hydraulics. I was hoping for something similar to the one mounted on top in the pic I attached. Can someone help me narrow down my options?