This extension spring is made of steel music wire and has an outside diameter (OD) of 0.42 inch and a wire size of 0.037 inch. It is made of highly magnetic steel music wire for greater strength than stainless steel. The spring ends are full twist loops for secure fastening. This spring has a load capacity of 5.2 pounds, and a maximum operating temperature of 250 degrees F (121 degrees C). It has an oil finish that is dry to the touch for added corrosion resistance. This music wire extension spring meets American Society for Testing and Materials (ASTM) standard A228 for quality assurance, and it is good for non-corrosive environment applications.

Extension springs are open-coil spiral (helical) springs that offer resistance to a tension force, or load, applied along the axis of the spring. When a load is placed on an extension spring, making it longer, the spring pulls back against the load to return to its original length. These springs are used in a variety of applications, including automotive engines, major appliances, medical devices, electronics, and sensitive measuring instruments.