My dogs love this thing! It's so much better and easier than treats. We especially use it while giving them a bath, and I think it makes them look forward to bath time. It lasts a while and you can't beat the price.
My dogs got into their VERY FIRST fight over these things. The problem is that two dogs can't enjoy them at once, which means they get jealous when you switch to the other dog. Yeah, they got so obsessed with it that they started fighting for real over it. You have to get out one for each dog or prepare to break up a fight.
I really wanted to love these, since they are low calories and easy to have with you at all times, but I found the ball didn't roll very well and I ended up having to move it myself. My dog LOVES his, but I'm a little disappointed.