Product Description This extension spring replaces most 7 ft. residential garage door springs. It features a 1/8 in. galvanized carbon steel cable that is installed through the spring to prevent injury in case of breakage. This spring is rated at 10,000 cycles. From the Manufacturer This extension spring replaces most 7 ft. residential garage door springs. It features a 1/8 in. galvanized carbon steel cable that is installed through the spring to prevent injury in case of breakage. This spring is rated at 10,000 cycles.