There are many options and styles to choose from. Here's a UTG Pro that replaces the original hand guards and has screws to hold the halves together. The down side to quad rails is they add weight as do all the goodies you may attach.
The hand guard here is a Magpul MOE. It also replaces the original hand guards, but comes with the ability to attach rail sections where you want them, everything you need, nothing you don't.
This is a Troy Alpha battle rail. By replacing the standard front sight with a low profile gas block and removing the Delta ring and spring, this free floats the barrel. It also provides the ability to attach rails only where you need them. Free floating the barrel also allows you to put longer hand guards on your rifle.
There are many, many other brands and styles to choose from, it's just a matter of finding what you want. Cruise the picture thread, as just about every option known can be viewed there. Shoot your rifle for a while and get a feel for what you need, then what you want.
Good Luck and shooting.
