Kryptonite's Evolution Series 4 1055 Mini Integrated Chain is a 10mm-thick, six-sided link chain made of triple-heat-treated, boron-manganese steel for maximum strength. At 21.5 inches long, the Evolution gives your bike security in a pint-size package. The links are covered with a weather-resistant nylon sleeve that protects your bike's finish, and it uses an integrated high-security cylinder that is pick, drill, and cut resistant. Three keys are included, including one that has a high-intensity LED bulb for convenient, easy unlocking in the dark. This chain has an anti-theft protection offer.