IN MOST CASES, NO BRACKETS OTHER THAN THE ONES INCLUDED WITH YOUR CONTROL400 SERIES SPEAKER ARE REQUIRED. Everything needed for most installations of these loudspeakers is provided with your Control Contractor ceiling speaker. However, a particular procedure that is sometimes used for installation into sheetrock (typically gypsum board) can be facilitated by the use of JBL’s optional pre-installation brackets before the sheetrock is installed. The pre-installation bracket provides a bracket to which wiring can be strapped in-place behind the sheetrock. It can function as a cutout template when many cutouts are to be made in a production-line style installation. And it can reserve a location in the ceiling prior to the sheetrock getting installed. The optional MR PLASTER-RING BRACKET (or “Mud Ring”) contains a circular offset, forming an edge guide for sheetrock plastering. The bracket has wings that attach to the building structure. Sheetrock is typically either precut or cut with a rotary cutting tool using the outside of the plaster ring circle as a guide. The sheetrock hole is then plastered (or “mudded”) up to the ring to create a seamless cutout.