Hand/Eye color coordination, finger dexterity, and non-sequential stacking capability, can all be measured with the stacking Sandwich. There is no right or wrong way to stack any of them, just let the child use its creativity and imagination to create their very own masterpiece. Non-toxic with a stain-like finish impregnated into the wood. Washable in the sink and is tub safe. Also ideal for use as trivets and decorative hot plates and coasters.