My 12 year old cat has stopped sicking up fur balls which she was doing on a daily basis. This product started working 3 weeks after using it. I am very pleased with the product plus the dry cat fur ball they also sell.
Thankfully my cat loves the fishy flavour and it did really help her with the hairballs, though it is not instant it did stop her being sick. So I would recommend it. My cat is just 3 years old.