Does the trick for crystals and FLUTD
Our poor little man had a terrible 2015, culminating in full blockage and a major operation (and month of sheer hell) in January.
However, having been told by the vets that he needs a crystal controlling diet now - perhaps for life - we started him on this (and the other flavours). He gets bored of flavours, so we alternate this, moderate calorie and beef (please start stocking beef zooplus!) plus the occasional katovit pouch. No bladder problems since the switch in diet. Great stuff.