The ABUS granit x-plus is a pretty tough u-lock for sure. To help explain the shearing action of a bolt cutter as related to the shape of the target (chain, shackle, u-lock, cable) I would like to submit the following two (2) images:



Yes, the trapazoidal target has a very large surface contacting the cutter blade. Making it more difficult to initiate the "shearing" action, which a bolt cutter depends on to make its cut. When it comes to mechanical stuff, the Germans and Austrians are some pretty crafty engineers...