Molymod Molecular Model Sets - Inorganic-Organic - Molymod MMS-009, Molymod Molecular Model Sets are the original dual-scale, quality system of molecular and atomic models.Scales: Open / Ball & stick models: 2.5cm / Angstrom, Closed / semi-space filling models: 1.5cm / AngstromAtom-parts: range from 17 to 23mm in diameter.Bonds: Single bonds are represented by medium links (19mm) and multiple bonds by longer, flexible links (30mm). For compact models, bonds are represented by short links (2mm).Valence: Represented by the number of holes: 1 hole (I), 2 holes (II), 3 holes (III), 4 holes (IV), 5 holes (IV), 6 holes (VI) Molymod MMS-009 Inorganic - Organic Student Set - 52 Atoms, 37 Links