They are #6's they fit better on this smaller layout and the largest locomotive I plan on running is a F7. The #6's go with the 8" radius curves too. BTW 8" in Z scale would be about 11" in N scale. This 2'x4' layout would be about 33"x66" in N scale. I don't have a lot of room, actually building this layout on the kitchen table! So that is part of the reason for trying out Z scale.