4 years & up. Encourage exploration and creativity with this wonderful Crayola® Non-Hardening, Colorful Modeling Clay. With four colors (red, green, blue, and yellow) at their disposal, children will love making animals, bugs, people, buildings, and more. This set promotes sensory learning, color recognition, and creativity. The clay stays soft for continued use. Available in a single box or a set of 12 boxes. Nontoxic. Each piece of clay weighs 4 oz.