Kryptonite evolution series 4 1090 chain lockfor times when you need the highest protection but do not have the space to transport a hefty u lock this heavy duty chain lock is perfect it is gold sold secure rated and made from 10mm steel chain links for the maximum protection as a leader in action sports security and the creator of the original bicycle u lock in the bicycle security category in 1971 kryptonite offers premium quality security products features the evolution series 4 integrated