Kryptonite Keeper 585 Chain Lock Black is an excellent choice for cyclists who are looking for a reliable and safe way to protect their bicycle against theft. This lock is made of hardened carbon steel and has four-sided links of 5 mm wide. The reinforced cylinder provides extra protection against lock picking and other burglary attempts. In addition, the lock comes with a nylon protective cover to prevent scratches on the bicycle and extend the life of the lock. With a length of 85 cm, this lock is suitable for most bicycles and can easily be attached to a post or other fixed object. It comes with two ergonomic keys so you always have a spare if you lose one. With a security level of 4/10, this lock is ideal for daily use in an urban environment. It provides sufficient protection against opportunistic thieves and is an affordable option for cyclists who want to protect their bicycle.