Almost all U.S. LTL carriers use NMFC freight classes, although some are attempting to move to a dimensionally-based system.
Freight Class 500 freight is the most expensive to ship. This classification is reserved for items of very high value or for items that use lots of space but weigh very little.
NMFC freight classes are determined using four factors: density, handling, stowability, and liability. All of these factors affect the cost to the carrier of shipping goods.