2 years & up. Six hardwood stacking squares feature inset colored acrylic windows for stacking, sorting, building, sequencing and creating imaginative, colorful constructions! Doubles as a stand-alone manipulative or an addition to hardwood block construction. Hardwood frames, rounded corners and edges, and inset acrylic windows. Largest square measures 7"W x 7"D x 2"H. 6 pieces.