Gasket is a material made of paper, rubber sheet or copper sheet, which is placed between two planes to strengthen the sealing material, and is a sealing element arranged between static sealing surfaces to prevent fluid leakage. Since the machined surface cannot be perfect, the irregularities can be filled with spacers. Gaskets are usually made from sheet materials such as pad paper, rubber, silicone rubber, metal, cork, felt, neoprene, nitrile rubber, fiberglass, or plastic polymers such as Teflon. Gaskets for specific applications may contain asbestos. Gaskets can be divided into non-metallic gaskets, metal gaskets, and metal-non-metallic composite gaskets according to their materials and structural characteristics, and each type can be subdivided into several types.