RD stands for Reduced Depth – so this speaker will fit into tighter spaces than the standard CCM663. A shallower cone and a redesign of the easy-fit QuickDogs™ frame reduce depth to a more usable 92mm, while retaining everything that makes the CCM663 such a great In-Ceiling speaker. The familiar, yet discreet, dark blue Kevlar® cone of the bass/midrange driver delivers a stunningly clean, detailed response. This, combined with the pivoting aluminium dome tweeter for adjustable off-axis treble response and three-position EQ, make this one of the most versatile custom speakers around. If preferred, the supplied round grille can be replaced with an optional, square CCM663 grille.