The 21 tonne mineral wagon served an essential purpose in the early stages of British Railways control over the new national railway network. These wagons were essentially coal wagons, the logical evolution of the old 3 – 7 plank wagon designs of the grouping era. These wagons were use for industrial scale coal transportation, with long trains of these being one of the only ways of transporting coal from the coalfields in the quantities required to keep the British steam train fleet running.

These wagons were of all steel construction with common yet uprated leaf springs to accommodate the load weight these would commonly haul. These wagons were fitted with side doors, to aid in the ease and speed of unloading the cargo.