This is the one I have on my personal Sport II
MOE SL(R) Hand Guard, Carbine-Length – AR15/M4
With this one, the installed sling mount has to be removed. They do make one that is shorter and allows use of the existing sling mount. There are other brands available, some of which will require modding/removal of the front sight assembly. Just google M Lok hand guard, and you'll see what I mean.
With the M lok system, you don't need the add on rails. This will explain how it works.