High quality materials: made of iron and galvanized. These butterfly shaped washers are sturdy, firm and not easily deformed, they are the highest quality four claw seals you can find in the market. They are durable, anti-wear and anti-corrosion. Enjoy reliability and quality with these fixing washers Seamless Application: When secured with the appropriate steel screws, our perforated thin metal washer adheres firmly to the surface. The perforation of the fixing disc allows the adhesive or plaster to stick to the surface of the board, minimizing the risk of delamination or surface damage. Used for insulation board, tile backing board, plaster board, composite board, extruded board, backing board on tiled floor or just for attaching building board to frames EASY TO USE WASHERS: These heavy duty fixing washers are a must have for installing tile panels. These fixing discs have been specially designed to provide an easy and secure way to help fix backboards and insulation boards to the floor and walls of the most common materials (wood, concrete, thermoplastic panels and construction materials). Synthetic insulation Package includes: Each pack of 200 easy to fit heavy duty steel washers which are 28mm in diameter, and usually 8 washers per plank are required, although this depends on the size of your back panel