We gave it to our son at 5 months. He's 7 months now and still loves it. He chews it, he puts it on his feet, he shakes it and it makes a bit of noise because of the small rings shaking.
I love then we can easily wash it in the sink and then sterilize it (not in microwave!) if he drops it in public places. And really he doesn't drop it often because it's so easy for him to hold. I'm actually quite surprised by this toy