The 900mm x 900mm VELUX ZZZ 210U Frame Fixing Kit is designed for mechanically fixing roof materials to a flat roof window base unit. This kit is ideal for roofing materials that do not adhere to the base units. This mechanical fixing kit is compatible with VELUX C-U base units and can only be used with these units. VELUX provide a 10-year guarantee on roof windows and a 5-year guarantee on electrics. Features & Benefits Ideal for VELUX C-U base units Designed for roofs that don't adhere to the bases