The sensory building blocks set contains 16 pcs Set is a vivid, exciting way for children to 4 shapes in 4 color and with 4 different materials. These smooth hardwood blocks feature transparent windows of strong acrylic in beautiful red, yellow, blue and green with different materials inside beads, liquid, sand and acrylic. Looking through the colored panes transforms a child’s world as the principals of light and color are discovered. These wooden blocks add fun, beauty and new dimensions together. This product helps with the development of hand-eye coordination, visual perception and can be used with a light panel or light table.