The K-SLC / K-SRC / K-SPC baffles are intended for installation inside square ducts when fabricating a ducted silencer. When installed according to the arrangement of the SLC silencer, the baffles provide the same sound insulation performance. The baffles can be installed during the assembly of the main ventilation ducts or after the installation of the whole ductwork by removing the relevant ductwork sections. The baffles are installed by inserting, aligning and fastening them with WGO self-drilling screws.