The Monitor Audio CMBOX-R (regular) is a Back Box made from MDF & has been designed to enable you to install their " Slim" " Core" & " All Weather CI" range in-ceiling speakers with a little more ease. This Back Box is compatible with Monitor Audios following custom installation speakers CS160 CS180 C165 C165-T2 C265 C265-IDC C265-FX AWC265 AWC265-T2 C180 C180-T2 C280 C280-IDC C380-FX C380-IDC AWC28 & AWC280-T2.