The CWM664 has the same basic features and dimensions as the CWM663, but uses a soft dome Nautilus tube-loaded tweeter instead of an aluminium dome, and a black glass fibre bass/midrange cone instead of blue Kevlar®. Installation is just as easy, thanks to our new QuickDogs™ fixing system and plug-and-play connection. Description 2-way in-wall system Drive units 1x ø25mm (1in) Nautilus™ tube loaded aluminium dome tweeter 1x ø150mm (6in) black glassfibre cone bass/midrange Frequency Range (-6dB) 45Hz – 35kHz Maximum Amp Power 25 – 130w Sensitivity SPL (2.83V, 1m) 87.5dB Impedance Nominal (min) 8Ω (4.5Ω) Frame height 315mm (12.4in) Frame width 221mm (8.7in) Cut-out height 279mm (11in) Cut-out width 183mm (7.2in) Depth behind surface 95mm (3.7in) Protrusion 4mm (0.2in) Pre-mount Kit PMK W6 Back Box BB 6W