I have the medium size I use on my GSD and my two cats. It works great on all of them. My one cat is part Maine **** and was constantly getting hairballs from his coat and the other DSH would get it when he licked the other too much. Now that I brush him out once a week, I haven't seen a hairball in a few months!And for my pup, it works great at keep her from sheedding too much and she looks all shiny and sleek after being brushed. I use it once a week on the cats and 2 x's a week on the pup.