HIGH QUALITY MATERIALS: Made of iron and galvanized. These butterfly-shaped washers are sturdy and not easily deformed, they are the highest quality four-claw seals you can find on the market. They are durable, anti-wear and anti-corrosion. Enjoy reliability and quality with these fixing washer discs SEAMLESS APPLICATION: When secured with the appropriate steel screws, our perforated thin metal washer adheres firmly to the surface. Used for insulation boards, tile backer boards, gypsum boards, extruded composite boards or simply attaching building boards to frames EASY TO USE WASHERS: These heavy duty fixed washers are an essential part for installing tile backer boards. These fixing discs have been specially designed to provide a safe and easy way to facilitate the fixing of backer boards and insulating boards to floors and walls of the most common materials (wood, concrete, thermal boards and synthetic insulation materials< /p> PACKAGE INCLUDES: Each pack of insulating nail locking parts includes 100 packs of easy-to-fix washers made of heavy-duty steel, which measure 28mm in diameter, and usually 8 washers per board are required, although this depends on the size of your backing board