Underfloor connection boxes are components of the screed-covered installation duct system. They are used at crossing points in screed-covered duct lengths and in the duct route, and, depending on the level of expansion, allow access to the cables in the duct or the installation of electrical resources. The box bodies are available in the system sizes 250 and 350 to match the screed-covered ducts. The box bodies possess internal height adjustment. Depending on the design, the box bodies can either be closed using a mounting protection lid (max. approved load 75 kg) or with a 4 mm-thick mounting lid with a blanking cover. The boxes are principally suited for use in floor structures in cement screed, poured asphalt and liquid screed.