Created and maintained by a nonprofit organization called the National Motor Freight Traffic Association (NMFTA), National Motor Freight Classification (NMFC) is a classification system used for interstate, intrastate, and foreign commerce movement of LTL shipments. You can learn more on our freight classes pages.
If the couch you are shipping has not been assembled yet and you are shipping various components that you can use freight class 250. If you are shipping a complete product then you should use freight class 175.
Density is the relationship between weight and size. A ping pong ball, which is very little material surrounding a good amount of air, is low density. Bricks, which are heavy for their size, are high density. In LTL shipping, it is commonly measured in pounds per cubic foot.