The N model railroad scale is one of the smallest popular train scales on the market. The N stands for nine, and refers to the track gauge - nine millimeters between the rails. These are smaller than HO, O, and other more popular scales, and work very well for people who have little room and want to enjoy the model train hobby in the space they have. They're also great for people who want to run extremely long trains. In general, N scale is smaller and lighter than larger scales, and requires less power.