We can further expand the Flory theory into a macroscopic view, where bulk rubber material is discussed. Assume the original dimension of the rubber material is L x , L y and L z , a deformed shape can then be expressed by applying an individual extension ratio λ λ i to the length ( λ λ x L x , λ λ y L y , λ λ z L z ). So microscopically, the deformed polymer chain can also be expressed with the extension ratio: λ λ x R x , λ λ y R y , λ λ z R z . The free energy change due to deformation can then be expressed as follows: