High quality materials: Made of iron and galvanized steel, these butterfly-shaped washers are sturdy, firm, and resistant to deformation. They are durable, wear-resistant, and corrosion-resistant, providing reliable performance for various construction applications. Seamless application: When used with appropriate steel screws, these perforated metal washers secure firmly to the surface. The perforations allow adhesive or plaster to bond effectively, helping prevent delamination and surface damage. Suitable for use with insulation boards, tile backing boards, plasterboards, composite boards, extruded boards, and for attaching building boards to frames on tiled floors. Easy to use: These heavy-duty fixing washers are designed for secure and efficient installation of tile panels and insulation boards. Ideal for fixing back panels and insulation materials to common substrates such as wood, concrete, thermoplastic panels, and other construction materials. Package includes: 200 steel washers per pack. Each washer has a diameter of 28mm. Typical usage is approximately 8 washers per plank, depending on the size of the panel.