TheMTC-81BB8fromJBLis a pre-install in-ceiling backcan designed for 11.25″ ceiling speakers, such as the 8138. It has an industry-standard mounting circle, and an extra-large volume to provide extra bass response. It has 5 conduit knockouts for running cables, and has the ability to nest during storage to minimize space requirements.

Designed to fit the 8138 in-ceiling speaker and the MTC-81TB8 tile bridgeIndustry-standard 11.25″ mounting circleExtra-large volume provides extra bass response5 conduit knockouts for easy cable installationNesting capability reduces the amount of space needed for storage