Developed by American Car & Foundry (ACF) in the mid-1960s, the 56' 4-Bay Center-Flow Hopper is ubiquitous across the North American rail network thanks to its robust design and versatile usage. Built to haul materials such as plastic pellets, animal feed, and other fine, granular products, the car was created with rapid loading and unloading in mind, coming equipped with four discharge bays on the underside of the body. Lasting in production until the early 1980s, the type remains a common sight on mixed freights throughout the United States, Canada, and Mexico to this day.