Plantoys 6 Piece Water Block Building & Color Mixing Learning Toy (5523) | Sustainably Made From Rubberwood And Non-Toxic Paints And DyesPlanToys Wooden Water Block Set consists of 6 water blocks in 2 shapes. Each shape has three different colors of water housed within the center of the blocks. Children enjoy watching the water swish back and forth and the blocks are super fun to use in a creative, imaginative way. When blocks are placed in front of each other, children learn how two colors can be observed to make a third. Science knowledge starts early! based on the 35 mm. block size.