The JBL MTC-30CM is a ceiling-mount adapter for the Control 30 installation speaker series. This mount allows the loudspeakers to be installed hanging down from a ceiling or beam. The adapter does not come with a base and requires the use of an existing Invisiball base, which is included as a standard accessory with the Control 30 speaker. Specifications: Compatibility JBL Control 30 Installation Speaker Series Package Quantity 1