Now I know why my cat has such big hairballs.
This tool seems to not so much take out loose hair, but 'trim' out the undercoat (so I'm not sure if it should be used on real outdoor cats as it can reduce the thickness coat a lot). It really is a different type of tool, and worth the money.
For an indoor cat it is fantastic, and you can take out as much as you wish... just know that that fur seems to keep on coming! I do it either outside, or probably better, in the bath so that the fur doesn't go everywhere. Honestly, you can't believe how much fur can come out.