Shipping International Harmonized Codes

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Hi - I'm working with a fulfillment center that is asking me to set up harmonized shipping codes for each variant for international shipping.  I'm not sure where I would input this. Has anyone come across this? 

"Please attach to each variant with harmonized code for shipping internationally. They have to be linked in items and are international codes for tariff changing customers.

For all upper body Shirts- Harmonized code 610910

For bags, harmonized code is 420229."