This one works.
Last October the vet advised me that the gut troubles our seven year old rescue cat was suffering were likely to be diet-related. "You get what you pay for", he said. Unfortunately, the wet version of z/d wasn't tolerated beyond about a quarter served beside three quarters of the usual food. As I'd never seen this cat drink any water, I didn't dare put him on a completely dry diet, but, see Royal Canin Gastrointestinal.