The pliers spanner replaces a whole series of open-ended spanners. In contrast to water pump pliers, the jaws grip the nut/bolt absolutely parallel. This is done over the entire adjustment range and without damaging the screw/nut. What they are completely unsuitable for, in contrast to water pump pliers, is gripping a pipe or nipple. These pliers spanners from Knipex are reasonably expensive, but they are also very precisely made. A great tool - I would buy the pliers again and again.