Diamond has the highest hardness and thermal conductivity of any bulk material while remaining an electrical insulator. The structure of diamond is based on a continuous network of tetrahedrally bonded carbon atoms in which extremely strong covalent bonds are formed between -hybrid orbitals. The C–C bond length is 154.448 pm. The crystalline structure is of cubic symmetry with unit cell dimension pm, containing eight carbon atoms per unit cell. The structure can be characterized as two interpenetrating face-centered cubic lattices, displaced by in each dimension.