I have a pit bull and a malinois and I got the large red ball for them. It is plastic so they can not pop it and that is what keeps them playing with it. My malinois is obsessed with it. I have to hide it so she calmed down because she is so dedicated to trying to pop it. These guys destroy toys and this ball is still going strong.
My German Shepherd, Katie, is obsessed with balls! She can completely destroy any toy she gets in minutes unless it's super tough! And these balls fit the bill! They are tough and durable, and provide hours of endless fun for Katie! They are self entertaining and she has a total blast with them! The only thing bad I can say (and it's not a big deal for us) is they are very noisy on hard floors and Katie can send them airborne by rolling them up a wall (so watch out breakables)! I would recommend them for outdoors play in a fenced yard or supervised, if you don't like the noise or have expensive figurines in the house. We designate "Big Ball" time and prepare accordingly :-) I have the 10" and will be ordering at least one each of the smaller ones. Highly recommend for aggressive and destructible players and chewers!
Both of my medium sized 50lb. pits love this 4 &1/2 inch ball! It DOES seem indestructible. It's just small enough that they can carry it, but just big enough that they can't get a solid grip on the ball either. It sounds like bulls bowling when it rolls across hardwood floors. I'm so far pleased, would purchase again.