Her favourite toy!
I bought them to go in the cardboard scratch mat/seat that I bought from Zooplus. They fit perfectly, she hunts them through the cardboard holes, but she also loves them when I bounce them at her, so she can catch them or chase them or swat them around. They are her favourite toy, she'll play with them on her own, day and night. I gave some to a friend for her cat in Australia, her cat goes bananas for them too, I've just sent her more. Great toy at a great price. Happy cat = happy Mum.