HS code is short for Harmonized Commodity Description and Coding System. It's a list of numbers used by customs to classify a product and it is used to define the duties and taxes to be paid. 

The Harmonized code (HS) can be found on the FedEx Harmonized Code Search page, or the FedEx International Shipping Assist tool, both require a free FedEx account to access and use.

First, select the country/territory the order is shipping to. Then, input the product you are looking up in the "Search For" section (i.e. for algae, type 'algae', for medium, type 'media', etc.)