Speakercraft Sound Enclosures are optional and are intended for pre-drywall applications and provide a back-box for Speakercraft in-ceiling and in-wall speakers. These must be installed BEFORE drywall. They increase bass response, prevent audio from entering adjoining rooms, and provide fire rated enclosure (UL standard ASTME E-119). Designed for 16" or 24" center studs Fits all 8" series in-ceiling speakers (AIM8, CRS8, DT8, 8.2BAS) Will not work with AIM Wide Dimensions: 14" L x 10" W x 5 3/4" D (not including front mounting flange) Sold in singles (each)