http://btcpsyz7f6t7pwi62xb4xbiuljcoscd4l4mlk2obxprp6vqohow3dvqd.onion/international-shipments-customs
In addition, any item inside of that package has to have a tariff number attached to it (You can use this tool to find a tariff number for any item you're shipping by typing in its name into the search box). In other words, if you send merchandise internationally labeled as "Merchandise", the receiver of the package will have to pay any customs fees, tariffs, etc in order to receive their package.