I got the Furminator small size, 1 3/4 inch for use on my 16 year old cat. I must say that this didn't get any more fur off than the comb we had been using on her to begin with but there are things that it did do. It was definitely easier to get the fur on the top of her head and neck areas due to the smaller size. It did not seem to hurt her as she actually sat still for a much longer period of time and it did seem to make her coat much shinier. All in all, a superior product than the comb but I only gave it four stars because of the fact that it didn't actually elimimate more fur than the comb did. The thing to ask yourself is will the higher cost be worth the shinier coat. In my case, I'm glad I bought it.