Stack, balance, hop, toss, and organize these bold and colorful stones--the learning and fun is endless! This set of 6 rainbow stones is lightweight yet remarkably tough, perfect for both indoor and outdoor play. Crafted from eco-friendly EPP (expanded polypropylene) and produced using pure air and water vapor, each stone can handle up to 396 lbs of weight--but take care: sharp objects can damage the stones and affect their stability. German-engineered for quality and durability!