The Bowers & Wilkins CCM663RD are a pair of in-ceiling speakers for your integrated home audio requirements. The RD in the name stands for Reduced Depth. Some ceiling cavities in your home may not have the space for a standard size speaker. But at a more manageable 92mm depth you will find these may squeeze into those tight spaces. If you dont require the full 150W of power that the CCM662s provide then these speakers are most likely the best option for you. They still feature the same pivotable tweeter & EQ switch for the bass-mids as many of the other speakers in this range.