I'm building a super-lightweight carbine and am looking for a quality carbon tube that I can use to mount rails (if they are included, that's great too. I only need top and bottom) and cover my gas system.  It needs to be roughly 9" or longer, clear a low-profile gas block, and be free floating.  

I'm a regular guy, regular budget, etc.  I've looked around, but haven't seen anything that stands out.  If anyone is getting rid of one or wants to trade for other hand guards, parts, etc let me know.

Any suggestions?

Lancer makes what you are looking for, as does AP Custom. You can also work with Carbon Arms to get something made up around the JP or Firebird Precision barrel nut.

Lastly, there is always PRI.

Don't forget to check their actual weights-some IIRC, were as heavy as the metal ones, depending on configuration.

The lightest out there, hands down, are the DPMS CF tubes but have no mounts.

I and a friend have AP custom hand guards. They are really nice, comfortable, super light except they have no rail in the 12oclock position and no means of mounting one.

If one has an alternate way of mounting a front sight , or don't need one then I would recommend them.