My guys love the ping pong balls with the little shaker inside that Petco sells. However, I was constantly finding them crushed...I guess my guys have bigger mouths than I thought. Anyway, no other balls seemed to get their attention the way those ones did, they were so light and rolled so freely. One day I was at Target and I saw some plastic, practice golf balls, they turned out to be a great alternative. They are light, roll well, but are tough enough to withstand a chomp. So try looking for some plastic golf balls, your guys will probably love them. Amy [Posted in FML issue 3495]