An organization known as the National Motor Freight Traffic Association (NMFTA) publishes a list of freight class designations, codes, and subclasses for many commonly shipped commodities (https://classit.nmfta.org/). You must pay a subscription fee to view this list. For more information about freight classes for free on our freight classes pages.
The class determines the cost of the shipping. The lower the class, the lower the cost.
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.