Sacred Geometry has the Platonic Solids which are the "building blocks" of the Universe. Every physical manifestation from a flower to a building to a person derives from these Platonic shapes. Depending on the material of the set you have, depends on how it may work. IE, someone who has migraines like myself may benefit from the dodechedron (associated with the crown chakra) in Amethyst. Each set has 7 pieces.
Each piece is about 5/8"