The Rattleback (also called the Celt Stone or Celtic Stone) is a unique spinning toy that only likes to spin in one direction, counter clock-wise. If you spin it clockwise, it shakes, stops, then spins counter clock-wise. If you tap one end of it while it's sitting still, it will spin counter clock-wise. Each Rattleback comes in a package which explains how it works. Each Rattleback is 4 inches long, 1/2 inch deep, and 3/4 inches wide.