Each block uses the square root of two principle to generate BG3 (used in the BioGeometry Charging Tray and BG3 Ruler). The height of every cube is derived from the diagonal of a square. The tray base for the blocks can be used as a shape sorter toy, and younger babies will love to push the cylinders through the blocks with the special cut-out pieces! These toys are made of solid wood and finished with a 100% natural, unscented, food-grade, toy-safe wood butter product from Switzerland.