The most popular modelling scale in the UK is 4mm (or OO), with a wide range of track, scenics and accessories already available to support those looking to build their first layout and continue adding to their hobby. For those interested in narrow gauge railways, the main scale is OO9. These models are all 4mm scale (1:76) but run on 9mm gauge track.

Kits have been a mainstay of this scale for over forty years, but more recently ready-to-run items have been regularly available. Fourdees look to continue and enhance the sector by producing a wide range of locomotive kits for various chassis, as well as rolling stock and upgrade kits.