Wow.
My dogs are kept thoroughly groomed, using undercoat rake, slicker, various widths of comb, shedding blade, etc etc...thought there was not much more to come off them. I bought this as I wanted to try something else on my VERY hairy collie-type, but couldn't justify the £30 certain other tools cost.
All I can say is, wow...on first using this there was fur everywhere. Would say it's best to make sure the dog is thoroughly brushed/combed out first though, as otherwise this tool can be inclined to cut the topcoat, which isn't what you want. And my housemate has learned not to use it on tails!! :D Very effective as a tool to strip excess hair out of an already well-groomed and knot-free dog though.