High-quality materials: Made of iron and galvanized. These butterfly washers are robust, firm, and do not easily deform; they are the highest quality four-prong washers you can find on the market. They are durable, wear-resistant, and corrosion-resistant. Enjoy reliability and quality with these fixing washers. Seamless application: When fixed with the appropriate steel screws, our thin, perforated metal washer adheres firmly to the surface. The perforation in the fixing disc allows adhesive or plaster to bond to the board surface, minimizing the risk of delamination or surface damage. Used for insulation boards, tile backer boards, plasterboard, composite boards, extruded sheets, backer boards on tiled floors, or simply for fixing construction panels to frames. Easy-to-use washers: These robust fixing washers are a must-have for installing tile backer boards. These fixing discs have been specially designed to provide an easy and secure way to help fix backing boards and insulation