Grimm's Building Set CornerstonesA building block really has what it takes it allows tricky and surprising layering variations and develops spatial thinking. This is how new and various objects in different color patterns are created over and over again. In combination with our classic building materials, the Cornerstones reveal their true greatness. With their aid, the most diverse marble runs arise. This product is recommended by "spielgut" (good toy guide) 18 pieces in wooden