2 years & up. Add a new dimension to block play with these water blocks. The colored water inside the blocks will show children how water changes shape and how color relates to water. In addition to developing their fine-motor skills and creative thinking, these blocks will give children a better understanding of physics and colors. Rectangle blocks measure 4.5" across x 1.25"D. Half circles are 5.5"W x 2.75"H x 1.25"D. 8 pieces.