HSN stands for Harmonized System of Nomenclature. It is a system for classifying commodities created by the World Customs organization. U.S. LTL shipping, however, uses NMFC classifications instead.
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.
Some items, such as car transmissions, have a specific class no matter how heavy or big they are. This is called a fixed class. Items can be assigned a fixed class if the value and transportability very rarely change.