JBL MTC-424MR Mud Ring Bracket For Control 424C/T Loudspeaker - 6 PackDesigned to provide an optional method for installing your JBL Control 424C T loudspeaker into sheetrock ceilings, the Mud Ring Bracket is a pre installation bracket that can also function as a cutout template and circular edge guide for sheetrock plastering. By using this bracket's plaster ring circle, you can cut a hole in sheetrock and then plaster up the ring for a seamless cutout. The Mud Ring Bracket features wings that attach to the building