Grades K & up. Easily demonstrate number relationships on the whiteboard! Colorful, magnetic circles, squares, and counters are designed to demonstrate fact family and part-part-whole relationships for the entire class. Great way to build addition and subtraction skills. This comprehensive set includes 3 circle and 3 square number bonds (8" and 9 1/2" in diameter, respectively), 4 connecting lines, and 45 magnetic counters measuring 1 1/4" each.