There are many kinds of gaskets, different sizes, thicknesses, materials, and different functions. Washers refer to the parts that are cushioned between the connected part and the nut. Usually a flat metal ring, in order to protect the surface of the connected parts from being scratched by the nut, it disperses the pressure generated by the nut on the connected parts. The plastic gasket is manufactured by injection molding process. This molding method applies the principle similar to the syringe. The body of the syringe is the injection molding machine. The injection liquid melts the plastic raw material, and the finger pressure on the syringe is the oil pressure here. The pressure forces the material through a tiny hole called a 'gate' and into the mold, forming the material.