Almost all U.S. LTL carriers use NMFC freight classes, although some are attempting to move to a dimensionally-based system.
Working with a 3PL like Koho can help you accurately determine your freight class so you can avoid re-classification fees with the carriers. For more information on the freight class system, go to the National Motor Freight and Traffic Association.
NOI stands for Not Otherwise Indicated. This is used when a commodity does not have an NMFC code. In these cases, density is usually used to determine freight class.