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This is the organic chemistry set for student of the polyhedron molecular models. Since this set contains C(sp2), N(sp2), m(sp), S, and Cl atoms besides regular C(sp3), N(sp3), O atoms, it is possible to construct the accurate C=C double bond, benzene ring, pyridine ring, and amide group, etc. Of course, by using m(sp) atoms, it is possible to assemble the accurate C≡C triple bond.

Despite the affordable price, the 4th edition of this set contains the p-atomic orbital plates (2 green plates and 2 blue plates) and the orbital connectors (1 green connector and 1 blue connector), which are very important for studying the π-molecular orbitals of olefin compounds, e.g. HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital). For example, the π-bond of ethylene molecule is shown here. 

In the ground state (HOMO), the p-atomic orbitals of two carbon atoms take the same sign or same color (green/green or blue/blue) as shown, because of the bonding character,  where two p-atomic orbitals partially overlap each other. This overlap is represented by the orbital connector. By this π-bond, olefin compounds take planar structures, and hence there are cis- and trans-isomers. Since the orbital connectors block the rotation around the C-C σ-bond, they are useful for differentiating  cis- and trans-isomers. On the other hand, in the LUMO, two p-atomic orbitals take the opposite signs or different colors (green/blue or blue/green), and hence the anti-bonding force works. Therefore, the orbital connectors are not used.

Thus, this set is highly recommended for undergraduate students studying organic chemistry.