HOn3½ gauge
= HOn3½ gauge
{wiki=HOn3½_gauge}
HOn3½ gauge refers to a specific model railway scale and narrow-gauge track gauge. In this context, "H" designates the scale as "HO," which typically represents a scale of 1:87, while "n3½" indicates a narrow gauge of approximately 3.5 inches (or around 89 millimeters) between the rails.