- Open-top hopper cars have sloped floors leading to bottom dump hatches; typically designed so that weight capacity and cubic capacity are maximized simultaneously for key commodities
- Segmented in the market by cubic capacity, gate design, interior length, weight capacity
- Cars are designed for unloading of commodities that can easily pour through the gates at the bottom of the cars
- Used for commodities that are not sensitive to the weather: coal, non-metallic minerals, metallic ores, woodchips
Woodchip hoppers, a sub-category of open-top hoppers are specially designed to carry woodchips and are not typically used to haul other commodities. The sides of a woodchip hopper are thinner, and therefore lighter, allowing the railcar to be loaded with the largest possible volume of woodchips. Some cars are equipped with rotary couplers so that rather than dumping the woodchips through the bottom gates, the car can be flipped over and emptied from the top.