Ideal Security Garage Door Extension Springs are designed for standard 7' tall garage doors. They provide additional lifting power for manual and electric garage doors. Safety cables reduce the risk of damage and injury if the springs or fastenings break. These springs are for wood panel or fiberglass doors measuring 8 feet wide and 7 feet tall or for flush wood or aluminum doors measuring 7 feet wide and 7 feet tall. The springs should be replaced with the same size as the original. Our garage door springs are color-coded to indicate weight capacity. They are available in five different strengths: light blue for 85-95 lbs, green for 115-125 lbs, dark blue for 135-145 lbs, brown for 155-165 lbs, and gold for 175-185 lbs. All our springs are 25-inch long relaxed and 67-inch long when fully stretched. It's important to always change your springs in pairs to maintain proper balance and install safety cables. The only reliable way to select your replacement garage door spring is to weigh your garage door then choose the closest load rating of spring, do not use your old spring Outside Diameter to select a new replacement spring as they may vary from batch to batch due to variation in material and process of making the springs. In addition, other manufacturer may use different material and process to make their springs.