Fifty-four millimetres is the format figure collecting grew up in, the height in which historical subjects have been cast for generations. The pieces here run from Napoleonic Guard infantry to an early medieval warrior. Note that 54 mm is the height of the figure, not a scale; in practice it works out at roughly 1:32. Castings arrive unassembled and unpainted, to be painted as standalone pieces on a plinth.
At 54 mm the head is large enough to shade a face properly, and the figure still does not take over a cabinet, which is why the format has lasted as a first step into serious figure painting. Thinned model paints and a round brush that holds its point carry the whole piece; a pointed sable from the brushes section matters more than any paint range. Other heights are under ŘOP figures.