A tension coil spring is a mechanical component that elongates when subjected to a tensile load and returns to its original position due to its restorative force. Hooks (loops) are formed at both ends, allowing them to be connected to other parts. Some also possess the characteristic of reacting immediately even to a slight load due to their initial tension. The main manufacturing method involves helically winding wire materials such as piano wire or stainless steel wire with a CNC coiling machine, and then forming the hooks. After forming, heat treatment for stress relief and stabilization of spring characteristics, as well as surface treatments (such as plating and shot peening) for rust prevention and improved durability, are applied. They are utilized in a wide range of fields, including automotive parts, home appliances, and medical equipment, for purposes such as part return, retention, and shock absorption.