Analogously to TIS, the initial interface 𝜆 𝐴 marks the boundary in CV space between the reactants and all other configurations, and 𝜆 𝐵 indicates the boundary between the products and all other configurations. The pathway from 𝐴 to 𝐵 is described by crossing a series of intermediate interfaces 𝜆 ∶ 𝜆 𝑖 ... 𝜆 𝑛-1 , with 𝜆 𝑖+1 > 𝜆 𝑖+1 for every value of 𝑖.