A simple 2 part back box system for flush fitting single gang electrical items such as switches, sockets and sensors. The two part system prevents concrete entering cable ducting voids, eliminating any time consuming and noisy chopping out processes after the concrete has cured. All boxes are produced to match socket dimensions and fixing centres in accordance with BS4662:2006. For seamless cable routing use in conjunction with 25mm double skin flexible conduit EBC25 and slide nuts EB1224-99.