12 months & up. Wooden Rainbow Architect Rectangles include 7 sizes of nesting beech wood rectangles. Use for stacking and open-ended play as they lend themselves to STEM concepts like construction, spatial reasoning, patterning, as well as, inspiring creativity, language, and design skills. Perfect with the other Rainbow Architect products to extend play even further. The colors in the set are red, orange, yellow, green, blue, indigo, and purple. Measures 1.6"D x 4.5"L to 8.7"L.