The original Troy Industries Delta Rail is a great free float rail option for those of you who want an extended rail but are stuck with a fixed front sight base and carbine length gas system. It can even be installed without removing the muzzle device so it is perfect for those with permanently attached muzzle devices. Friend of JTT, Jon L, has one that he likes very much. I have been able to check it out in person and the way it attaches to your carbine with no modifications whatsoever is absolutely ingenious.
Now there is a new VTAC version of the Delta Rail that sports the recognizable elongated cooling holes for which the VTAC rails are known. It is available in black or FDE. You can check out the Troy/VTAC Delta Rail on VikingTactics.com or TroyInd.com.