7mm scale, also known as British O scale, is a model railway scale of 1:43.5 (or 7mm to 1ft; hence its name). The scale is thus different from American O scale (1:48) and European O scale (1:45). For standard gauge railways, 32mm gauge, or 0 gauge is most commonly used. ScaleSeven (S7) standard however specifies 33mm gauge, which is closer to scale. For narrow gauge modelling, 16.5mm gauge

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