Made of hard plastic so it's very noisy when rolling around and into things. My dog never took a liking to it. He pawed at it a few times and now it just sits in the room, lonely, waiting for a chance at redemption.I think the hard plastic lacks the "fun" while the magnitude ensures that they can't get their mouths around it. Not being a dog, I can't be positive, but I assume that "squish" and "ability to fit in mouth" are two relatively high priorities in the dog world and this lacks in both.