The first batch of LNER bulk grain wagons were built to a design based on existing GWR grain wagons, in turned based on conventional covered box van design and construction with an internal hopper sized to hold 20 tons of grain. The wagons were designed to be 'convertible', featuring two pairs of side doors along with a single roof hatch and underfloor hopper. The internal hopper was formed with folding panels intended to be folded down over the underfloor hopper outlet to allow the wagons to be used as conventional box vans when not needed for grain service. This quickly proved impractical for both companies, the vans needed to be substantially constructed to resist the loading of 20 tons of grain, including heavy doors with substantial screw bolts and the folding floor panels were too heavy for 'conversion' to be a regular option. The single filling hatch also made it difficult to adequately distribute the grain during loading to achieve a full load.

Grain traffic at Hull quickly grew to levels where the grain hoppers were permanently engaged on this traffic and more hoppers were required. Built as dedicated grain hoppers the side doors were eliminated and a twin hatch arrangement was adopted to price better load distribution. For internal maintenance a small access hatch was fitted one side, while small observation windows were added in the top corners at each end so staff could check if the hopper was loaded or empty. The older (and GWR) wagons were also modified with the doors eliminated and fixed internal hoppers, but retaining the single hatch.

Later GWR and LMS grain hoppers were all-steel constriction, eliminating the wood box van outline completely and leading to the British Railways grain wagon design of the 1950s. The original single roof hatch wagons were withdrawn from traffic early, however the later twin hatch LNER wagons modelled from this kit could still be found in regular use into the 1970s and several have been preserved.