My pigs love these balls. The balls have a center ball with a bell. The bell sound makes my pigs do the zoomies. They love to get spunky and play with toys. I recommend providing your pig with a lot of different toys to keep them stimulated and not bored. A bored pig is a vocal pig. The balls come in in two different colors and they are made of a hard plastic so they won't break apart. You can mix and match or get all of the same color. The diameter is 3.1". Please check out my other items you might find a few items I can ship together. I also have pig boxes full of various products.