Assuming no scattering and ideal (transparent) contacts, the conductance of the one-dimensional system is given by G = G 0 NT, where T is the probability that an electron will be transmitted along the channel, N is the number of the channels available for transport, and G 0 is the conductance quantum 2e /h = (12.9kΩ). Perfect contacts, with reflection R = 0, and no back scattering along the channel result in transmission probability T = 1 and the conductance of the system becomes G = (2e /h) N. Thus each channel contributes 2G 0 to the total conductance. For metallic armchair nanotubes, there are two subbands, which cross the Fermi level, and for semiconducting nanotubes – bands which don't cross the Fermi level. Thus there are two conducting channels and each band accommodates two electrons of opposite spin. Thus the value of the conductance is G = 2G 0 = (6.45 kΩ).