Surfaces are dry-erase compatible for the complete STEAM experience! Work well with all items on this page. Perfect size for homes, home-based day care, and multi-child play. Comes with STEM activity guide and free lesson plans online. 19 Piece Set includes 11 solid panels in red, yellow, green, blue and purple colors and 8 white windows. Pieces measures 9"x 9". Ages 3 and up.