The National Motor Freight Traffic Association (NMFTA) publishes a list of freight class designations, codes, and subclasses for commonly shipped items (https://classit.nmfta.org/). A subscription is required to view this list. You can read more about freight classes at Koho for free on our freight classes pages.
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.
If you don't include an NMFC code on your BOL, it is very likely that your carrier will charge you a reclassification fee and charge you the cost of shipping the freight they they determine your shipment is.