Are you referring to a mini 5 u-lock like this one:

https://www.amazon.com/Kryptonite-Evolution-Mini-5-Heavy-Bicycle/dp/B005YPK9C0

And an Abus chain like this one:

https://www.amazon.com/ABUS-10KS-Security-Chain-Sleeve/dp/B005UMCBL4

They do look pretty tough but that chain looks heavy. Maybe 2 u locks would do the trick. But now I would have twice as many keys to carry and that always makes me think I will lose them.