Product Description Heavy-duty (10,000 cycles) extension springs have double loop ends for extra durability. 5 sizes will replace most all spring configurations on residential doors that are no higher than 7 Ft. 1/8 In. Galvanized carbon steel aircraft cable installs. From the Manufacturer Heavy-duty (10,000 cycles) extension springs have double loop ends for extra durability. 5 sizes will replace most all spring configurations on residential doors that are no higher than 7 Ft. 1/8 In. Galvanized carbon steel aircraft cable installs throug