husband just came home with a box of sensory balls for the Tot Monster Twins. They took to them instantly. They are squashy, and easy to grip. The spines allow for easy spinning, rolling and other manipulation. Little Tyrannosaur spent a good hour just spinning a little one in his hands, and he's now watching a Thomas the Tank Engine DVD through a translucent one. Tyrantina likes to clasp one between her feet and roll it back and forth. And best of all, they're calm. No flapping, no squealing. Very cool!