Bose Professional Bose FreeSpace FS2C Retrofit Kit

FreeSpace FS2C Retrofit Kit: Retrofit hardware for dropping an FS2C into a ceiling that is already up. Compatible with FreeSpace FS2C in-ceiling loudspeakers.

Bose specifies it for existing ceilings. It ships under part numbers 842864-0110 (Black), 842864-0210 (White).