Expand your SmartMax creations and your creativity with this special extension set, which includes 6 metal balls for holding magnetic bars in place. SmartMax enables young children to explore magnetism safely, with strong, oversized pieces that are specifically designed for handling by young kids. At the same time, older children will have fun using the pieces to construct towers, bridges and countless other creations. SmartMax magnets are strong enough to carry up to 60 times their weight! Note the SmartMax extension sets are designed as add-ons to the basic sets. Each pack includes 6 metal balls to expand SmartMax creations.