The AAR Standard 50 Ton Flat Car was 53" 6" in lenght and had a riveted steel underframe. Based on the Union Pacific F-50-11 class design built by Pullman-Standard in 1941, its overhanger wood deck was supported beyond the side sills by steel angles and it had fifteen pressed steel stake pockets on each side. A distinctive feature of the design was its offset center stake pockets, which were located slightly to the right of center on each side owing to the location of the ceter underframe crossbearer. All told, hundreds of AAR Standard 50 Ton Flat Cars were built for a wide variety of railroads over a period of almost twenty years. In the 1950's and later, many were converted for trailer-on-flat-car (TOFC) service and others were fitted with end bulkheads for such loads as plasterboard or with special loading equipment for everything from automoibles parts to farm tractors. Some rmained in revenue service as late as the 1980's and a few survie today as maintenance of way cars