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.