The tension spring neutralizes the difference in tension in the wire caused by temperature fluctuations. It keeps the wire evenly tensioned in summer and winter, which means you can double (up to 15 m) the distance between the posts. Suitable for 2.5 mm and 2.65 mm HT wire and EquiFence. Maximum tensile strength 200 kg. Stainless steel, spring length 345 mm, product warranty 10 years.