This torsion spring is constructed of steel and it includes a stationary cone and a winding cone attached to opposite ends of the spring. These types of torsion springs provide lifting force for heavy garage doors and must be selected by the springs dimensions, rather than the doors weight. See the product specifications found in Prime-Lines Torsion Spring Selection Guide to assure that the proper replacement spring has been selected. With dual spring installations, note that the proper use of LEFT WIND and RIGHT WIND springs is imperative. Also, when dual spring installations are involved, it is important to replace both springs, as replacing only 1 spring may add increased strain to the older non-replaced spring. This torsion spring is a regular duty spring with an estimated lifetime rating of 10,000 cycles. Determine the handing of your torsion spring wind, look at the end of the spring with the finger of the spring at the top of the wind. When the end of the spring is at 12:00 o'clock and it is pointing to the left, the spring is a right wind; if the end of the spring points to right it is a left wind. When standing inside the garage looking out, the torsion spring with the black painted winding cone installs on the right side of the door, and the white painted winding cone installs on the left side of the door. As an important safety precaution: all broken or malfunctioning hardware should be replaced with matching hardware, without any modifications. These garage door torsion springs can cause serious injury if not handled and installed properly. If attempting to replace the torsion springs yourself, it is important that the removal or adjustment of torsion springs is not attempted with any other tool other than Prime-Lines item number GD-52238. Failure to utilize Prime-Lines item number GD-52238 for the replacement of these springs may result in severe personal injury. Make sure to replace the left side as well, Prime-Line part GD 12231.