QO Load Centers offer premium features like QO breakers, ground arc fault interrupters and surge arresters. QO load centers are designed for residential and industrial use to protect electrical systems, equipment and people. Systems are single or three phase and have indoor and outdoor versions. QO Load Centers enable the use of a full complement of accessories. Indoor enclosures are designed to be rotated 180 degrees to accommodate top or bottom service entrance feed. This QO OEM plug on mounting base is for 225A 120/240 VAC 1 phase 3 wire systems. This QO OEM mounting base has a 10 kA breaking capacity. This product is for 42 spaces. This mounting base will accept only QO plug on circuit breakers. This system is plug on neutral and has a neutral bus bar. The QON mounting base is UL component recognized.