HOn3½ gauge
HOn3 gauge represents the modelling of gauge railways in HO scale, resulting in a model track gauge of . Trains are operated using direct current or Digital Command Control over realistic-looking two-rail track.
Railways that use the gauge can be found in New Zealand, South Africa, Indonesia, Australia, Taiwan, Japan and others.
Manufacturers of Australian outline models in this size include Haskell Models, Wuiske Models, Black Diamond, PGC, Southern Rail and SDS Models. The main focus for Australian narrow gauge modelling has been the large Queensland railway system. More recent releases have included Tasmanian and Western Australian prototypes. In New Zealand, the scale has a few niche manufactures.
CMD models and SARModel produce South African and Zimbabwean HOn3 models.
Most Japanese and Taiwanese HO scale models are made to run on 16.5mm gauge track and are made to 1:80 scale but some small volume HOn3.5 kits and brass models are made for Japan with Imon being a major supplier.