QO Load Centers offer premium features by allowing QO breakers, ground arc fault interrupters arc fault interrupters and surge arresters to be installed inside QO Load Centers enable the use of a full complement of accessories. Systems can be single or three phase and have indoor and outdoor versions. Homeline load centers are designed for residential and industrial use to protect electrical systems, equipment and people. This accessory for QO and Homeline Load Centers is a bonding screw kit.