404# is an upgraded kind of snap button. It is combined by an plastic round spring, which solves the noise problem caused by buttons. It is divided into four parts from the top down including cap, socket, stud and post. The female side part is composed of cap and socket and the middle of socket is a hole with a round spring ring. The male side part is composed of stud and post and the middle of stud is a convex dot with a hole. The dot will be clamped tightly by the round spring ring when pressed into the hole of socket, producing a combined force to fix clothing.