The Structural Molecular Model Set contains a number of different colored plastic spheres to represent various atoms. The atoms have holes at specific angles to accept plastic rods representing covalent and ionic bonds. The set allows you to build structural models of over 40 compounds and a graphite crystal. Set includes 58 plastic spheres-23mm in diameter, 12 hydrogen atoms and 3 metal atoms-17mm in diameter, 43 short connectors and 10 long flexible connectors.