Gn15  Gn15 is a rail modelling scale, using G scale 1:22.5 scale trains running on H0/00 gauge () track, representing minimum gauge and miniature railways. Typical models built are between 1:20.3 and 1:24, or up to 1:29. ' NEM 010 specification defines IIp for modelling gauge. Gn15 modeling is a relatively new phenomenon in the model railroading world. While the idea of this scale has existed for some time, as evidenced by the early efforts of Marc Horovitz, editor of "Garden Railways" magazine, Gn15 did not gain any measure of popularity until the Sidelines range of models. Following the advent of these kits, a few other lines of kits became available. Initial community development took place on Yahoo email groups, but these have been superseded by the forums at Gn15.info as the primary form of communication between the far flung practitioners of this scale. Alongside Gn15 other modeling scales have developed to cover both the modelling of minimum gauge lines in scales smaller than G, and 'miniature' lines (less than ) in G scale. O9 or On15 is the use of N gauge track in 7mm scale to represent a 'minimum gauge' line. In comparison GNine is the use of 9mm track to represent 'miniature' lines. GNine is a 'flexible' term for scale, referring to modelling using garden railway scales and N gauge track. GNine models can be built to scales between 7/8" and 1:35 representing anything between gauge and miniature railways.