Go Pet Club has come out with a great way to keep you cats active. They have added an IQ Busy Box on several of their cat trees. These boxes help keep your cats mind sharp and active. Each box has several holes in the top and sides. Two balls are placed inside for your cat to move around. Not only will they be able to play on the cat tree, they will have the extra challenge of trying to get the balls out of the busy box. The cat tree has definitely evolved!