I have this lock, including the chain.



It's very practical. I can leave the chain at home and only have the very easy use of the 0-lock. I can use just the 0-lock with the chain wrapped around the frame, it stays locked in the 0-lock so it's not like the chain can be stolen, I have it wrapped around the underside of the saddle so my Brooks won't get stolen either. And I can wrap it around some tree or lightpole if I think that extra trouble is necessary.

These are good locks, both 0-lock and chain require an angle grinder to break and even with that tool it will take a while. You can choose between different plug in chain lengths up to 140 cm or a 180 cm cable, and they even have a saddle bag for the chain if you don't want to wrap it around the frame. Asus makes as comparable lock system, I assume it works exactly the same, because that's the best way.