… in concrete floors The XXL 306 large-format socket support box with mineral fibre board manufactured by Primo GmbH can be easily installed in concrete walls and floors in the precast facility. The socket box is suitable for installing light fittings, loudspeakers and other incorporable devices. The socket lid is secured to the formwork. After that, the upper part with its sturdy steel lid is fitted. Thanks to the robust metal plate, no support tube is necessary. Structural stability is not affected, since the slab reinforcement passes under the transformer tunnel. Then, the installation pipes or cables are inserted into the socket box, the upper reinforcement is laid over the socket and the floor slab is filled with concrete.