6t sb, support box, intended for use when installing chimney in a frame, in a mobile home, or in a ceiling under a narrow section of roof, provides a finished installation at the ceiling level & will support up to 20' of a 6" diameter chimney, also provides shielding from insulation when installed in an unoccupied attic space, assembly is comprised of a black box designed for installation inside 16" o.c. Joists, a cylindrical shield, support bucket, ceiling trim & 4 screws.