MTH: 30-75731 RailKing Union Pacific Airslide Hopper Car #20459 O Gauge General American Transportation Corporation produced more than 5,000 4180 cubic foot Airslide covered hoppers between 1963 and 1980 as a response to customer demand for larger covered hoppers capable of handling bulk commodities. These very common cars continued General American’s “Airslide” family innovations from the 1950s, and proved valuable to bulk shippers who wanted a larger car than the earlier-design 2600 cubic foot cars provided.In an Airslide covered hopper, the bays are formed into two narrow, steep-sided troughs with a layer of air-permeable material at the bottom. Air is pumped through the material causing the load to fluidize and flow easily through the hopper outlets.High quality, traditionally sized RailKing Freight Cars provide detailed bodies and colorful paint schemes for the O Gauge railroader. MTH makes an enormous variety of RailKing Freight Cars, including many different car types and roadnames. No matter what era or part of the country you are modeling, RailKing is sure to have something for you.