Fibaro FGS221 The Fibar insert is designed to be placed into a pattress box behind the traditional switch. This switch is then not longer controlling the electrical load directly but acts as input device for the insert. The insert has an internal relay to control the electrical load attached. With product an existing installation can be turned into a Z-Wave enabled smart system keeping the original switches in place. This is particularly important if these switches belong to a special switching series where no Z-Wave enabled replacement is available. However the pattress box need to be deep enough to accommodate the insert and the traditional switch. The insert is 15 mm high so a minimum depth of about 50 mm is required to install the product.