Shure A900-CM - Ceiling Mount for MXA900 Series Ceiling ArraysThe A900 CM Ceiling Mount allows Shure ceiling array microphones to be mounted to a drywall joist, plywood joist, or concrete ceiling, or a 4 inch octagon junction box. Its two piece design makes installation straightforward. The included ceiling plate attaches to a joist, the concrete ceiling, or a junction box. The ceiling adaptor plate attaches to the top of the microphone. The two plates then slide together and are secured by a hex screw.