Brilliant
I use this ball not as a "slimming aid" but to keep my cat busy. I don't use it every day.
My cat (I have 2, one is quite fat and totally indifferent to this product, the other is very slim and loves this) always asks for food and can sometimes be very noisy and gets quite agitated, so I give him this ball to roll around with 6-8 tiny treats inside and it seems to calm him down.
I think this is a brilliant product, you can use it with any kind of dry food because you can adjust the gaps to adapt to the size required.
My fat cat is not interested in the ball, probably thinks it's too much hard work!!
I bought a second one for my mum's cat who is old and needs some indoors activity.