A rubber flat washer is a type of rubber gasket that is flat, circular, and has a hole in the center. It is designed to provide a cushioning effect and prevent leaks between two surfaces, such as nuts, bolts, or screws. Rubber flat washers are commonly used in plumbing, automotive, and mechanical applications. They are often made from materials such as neoprene, silicone, or EPDM rubber, which are flexible, compression-resistant, and have good chemical resistance. Rubber flat washers can also help to reduce vibration and noise, improve sealing, and prevent damage to surfaces. They come in different sizes and thicknesses to fit various bolt diameters and applications.