Basically, the KEIL undercut anchor is an anchor with a "displacement-controlled assembly". For the segments to fit snugly into the undercut, they have to be "folded out" with the aid of a screw or a threaded pin. The high assembly safety of the KEIL system is demonstrated by the fact that this is only possible with correctly undercut drillings.
A restriction of the tightening torque value will ensure that mistakes are recognized even for incorrect drillings or too short undercut anchors and that the assembly will be safe at all times.