5 yrs. & up. Heavier or lighter? Taller or shorter? Compare linear measurements and use the tree-themed balance to compare weights. Balance arm snaps into place for quick assembly. Calibrates easily with sliding compensator clips. Balance measures 15.75"L x 4"H. Grades: K+. Includes: 24 caterpillars in two sizes and two weights (8 large, 16 small), 36 leaves in two sizes and two weights (12 large, 24 small), and Activity Guide.