Funny thing, turns out cats love the crackling sound these things make! Who knew? I remember my older cat used to grab the cellophane packaging on products I bought, and he went crazy over the crinkling noise, so I guess it makes sense that cats would go for these, too! A great toy for cats of all ages. The balls are about 2" in diameter. Four in a pak, and they come in assorted colors, which may vary.