Insane
Our cat goes absolutely crazy for this thing, he doesnt play with it he goes into full on hunting mode like hes chasing an actual critter. He could chase it for hours without a break if we let him. Definitely a 10/10 purchase. However you need to supervise all playtime with it because if your cat likes to bite, chew or carry toys in their mouth then the worm is gonna lose some of the "fur" and the cat will try to eat it. You can find replacement worms online so thats nice.