Editing 4 mm scale (section)

===OO gauge===
[[OO gauge]] uses 4&nbsp;mm scale with 16.5&nbsp;mm [[Rail gauge|gauge]] track,<ref>{{Cite web |title=Standards |url=https://doubleogauge.com/standards/ |access-date=2022-03-31 |website=The Double O Gauge Association |language=en-GB}}</ref><ref>{{Cite web |date=2019-06-07 |title=What is OO gauge? |url=https://www.world-of-railways.co.uk/techniques/what-is-oo-gauge/ |access-date=2022-03-31 |website=World Of Railways}}</ref> which is inaccurately narrow since it is correct for [[HO scale]] (1:87.1). It is the most popular standard in the UK for 4&nbsp;mm scale trains<ref>{{cite web |title=OO gauge |url=https://www.fabtintoys.com/oo-gauge/ |website=Fabtintoys |publisher=Fabintoys |access-date=12 April 2022}}</ref> and is produced by the two main manufacturers in the UK. The traditional standard for wheels and track is a very coarse one with extremely oversize [[Rail tracks|rail]]s and [[flange]]s; in recent years, some manufacturers have switched to using the American [[National Model Railroad Association]] HO standard S-4 instead.