18 months & up. Blocks that have color mixing properties when on a light table? Perfect! Made from transparent silicone, these interlocking bricks are flexible and an ideal first construction set. They can be used inside or out and are great for light table and sand/water play. Pieces may be washed by hand or in the dishwasher. Bricks measure 3"L x 1.5"W x 1"H. Set of 24.