You see, any lock is defeatable, but having said that, the aim is to frustrate a would be thief, if your using two different locks to lock your bike a thief is not going to want to carry two different set of tools. While a battery powered angle grinder can make fast work of any lock it will also make a lot of noise and most thieves do not like that kind of attention. Picking on the other hand makes no noise, there are no large hand tools, and it just looks like someone have difficulty with their key...but this type of theft is not popular-yet. So combining a U-Bolt with a chain or a armored cable along with Pitlocks is to frustrate a thief to the point he's going to leave and go after an easier target.