21.5 cu. in. Fan Box allows you to safely install your ceiling fan or lighting fixture without having to access attic space. The side bracket box design provides secure attachment to an existing ceiling joist. It is ideal for installation during new construction or remodeling and can be installed in finished ceilings through a hole large enough to fit the box. The Side mount features a heavy-duty, all-metal, 2-1/8 in. Deep, dual-mount electrical box. To install it in a finished ceiling, simply mount the bracket to a joist through a 4 in. hole in the drywall, pull the wire into the box and remount the box to the bracket. The Side mount bracket is removable for easy replacement of existing nail-on boxes without attic access. The kit is UL listed to support fans up to 70 lbs.. and light fixtures up to 150 lbs.. It includes 10-24 threads for heavier fans and fixtures and 8-32 threads for cover plates and lightweight lighting fixtures.