These are plastic molds that make your eggs shaped like a golf, tennis, or soccer ball. They were designed by Avichai Tadmor and now being sold over at Monkey Business for $12.
Basically you just boil an egg, peel it, pop it in the mold until it cools and presto! You’ve got an egg shaped like a ball. Not entirely sure why you’d want an egg shaped like a ball, but I’ve heard of crazier things. I can’t think of any now, but I’m certain I have.