I use this for my parakeets. They love the bell And climb on the ball. I had seen this filled with hay and birds were pulling it out and playing with it. I will do this once I place it inside cage. Will definitely keep them busy. Good product.
I stuff the hay ball up twice a day for each guinea pig (I foster for rescues). They seem to enjoy eating from it rather than off the ground. I stuff hay in from various slots so they don't yank the whole thing out with one tug. Hard hay stalks don't stuff well in it.