3 years & up. These wood-framed blocks add a new look to block play. Each set includes 4 square blocks and 4 half circle blocks. The colored water inside the blocks helps children learn about water as it"s shape changes with the movement of blocks. Looking through these blocks children get another perspective of the environment. These blocks work well on light tables. Square blocks measure 4 1/2" across x 1 1/4"D. Half circles are 5 1/2"W x 2 3/4"H x 1 1/4"D.