The KI-RB4 mounts to North American 4 inch sq. electrical boxes. It includes the GSA-TS4 Trim Skirt, which is used to cover the -œmounting ears" on the base. Detector mounting bases have wiring terminals that are accessiblefrom the -œroom-side" after mounting the base to the electrical box. The bases mount to North American 1-gang boxes and to 3 1/2 inch or 4 inch octagon boxes, 1 1/2 inches (38 mm) deep. They also mount to European BESA and 1-gang boxes with 60.3 mm fixing centers.