Steel-O-Chain 9809K XPlus

Chain locks are flexible and strong, allowing you to lock up in a higher variety of places. Combine it with a U-lock and you won't need to worry about your bike.
 
9mm strong square chain
The chain, housing and structural parts of the locking mechanism are made of hardened steel
ABUS Plus Cylinder
Automatic keyhole cover to prevent corrosion and the ingress of dirt