The Bowers & Wilkins BB 125C Back Box is an insulated enclosure for any speaker from the CI300 range as well as the reduced depth CCM663RD. This box will define the perfect amount of space needed for an integrated speaker. This particularly will be useful for concrete-filled ceilings. Providing both sound insulation for adjoining rooms & insulation from fire this is a must have for many building regulations if you are building an audio system with a newbuild house.