New or used and "WITHOUT" UPPER receiver, unless its an vltor MUR-1A. If you happen to have an upper with the MUR-1A,that would be preferred. and "if" it happens to have a troy 15",DD 14" OR Larue 13.2" rail already installed(I know It's a long shot but It's worth throwing out there) that would be a huge plus as that is what I'm looking to build.thanks