So this set, one is hollow & 1 is solid. The hollow one is great for freezing a snack inside. As long as it has a filling of some sort, my dog loves it. If he empties it, I have to get it away from him fast. He then bites chunks of rubber off the sides. The solid rubber one has held up much better. I think the set is great. It offers 2 different entertainment options. I just try to swap the flutes quickly when the hollow one is empty. It washes up great in the dishwasher too.