Engineers start here! This unique set is packed with interlocking disks—for open-ended construction that develops spatial thinking, coordination and dexterity…and lets imaginations run wild! The pieces come in 12 different colors and are a cinch to click together and pull apart—for endless design possibilities. Set includes a jar of over 500 pieces made from durable polyethylene, plus a mini idea booklet with instructions on building a rainbow ball. Disks measure approximately 1 1/4" in diameter.