16.5mm gauge track in 7mm scale gives an equivalent prototype of 2ft 4 ins, making it a popular choice for modellers, this scale is also known as 0n30 in the USA because this results in a prototype gauge close to 30ins. many modellers find that this scale/gauge allows an ideal combination of scale detail in a relatively small space. For more details on Electrofrog turnouts, see our Wiring the Layout publications Nos 4 and 21.