Fitted with motor mounted on silent elastic blocks, this fan delivers incredibly quiet running and exceptional performance with stylish features. This model has a built in PIR Movement Sensor which automatically switches the fan on when movement is detected, then off after a pre-set time. Features: Sealed for life ball bearings Silent elastic blocks IP45 rated Backdraught flaps Dimensions: 158mm wide x 158mm high. Spigot is 99mm diameter (for connection to 100mm ducting) and projects for 80mm beyond installed surface.