The DuraTech 6" x 24" Class A Chimney Pipe Square Ceiling Support Box is used to support chimney pipe and provides a positive connection between support box and chimney with a built-in twist lock. Suitable for both flat and cathedral (A-Frame) ceiling applications. Also is used in short attic spaces (see instructions). Fits between standard 16 on-center joists and most manufactured home applications. Supports up to 60' of DuraTech Chimney. Use adapter to attach DVL or DuraBlack to the support box. A 2 wide trim collar is included. Painted black.