they're completely customizable for each individual user. you can change palm rest height, how far away the buttons are, weight, etc. one of the parts i love that i've never seen on a mouse before is the "sniper button". it's a little red button you can hit with your thumb when playing fps. it temporarily reduces the dpi so your cursor will move slower on screen... perfect for a headshot.
the r.a.t. 7 is the same thing, but it's the wired version. it goes for $100.