Paw pods, balance balls, balance cushions or half balls. Regardless of the name, they are basically the same kind of balance ball. Just different sizes. Some with spikes and some without. Which half ball is best is more a question of what kind of dog you have and how you plan to use the ball. The half ball gives the dog good balance while the dog effectively exercises both paws and wrists. To train the whole body, you can either have balls under each paw or use, for example, a sleeping cushion under two paws.
Balance ball training can also be an effective rehabilitation training for the animal. But if your doggy has been injured, our tip is that you check the training with a dog physiotherapist.