The other NEM defined narrow gauges for H0 scale are H0m (using gauge originally TT scale track) for models of gauge and similar prototypes and H0i (using Z scale track - also known as H0f) for prototypes around - the most popular gauge for industrial (or Feldbahn) railways.
In the United States the NMRA have developed many standards[REF] for narrow gauge modelling, including those modelling in HOn30 and its related gauges.