Review this post
http://advrider.com/index.php?threads/givi-trekker-outback-37l-panniers-cases-review-long-book-version.998276/
Lots of info regarding tariffs. There are no tariff charges for Motorcycle Accessories, keyword being
Accessories. Plastic or metal doesnt matter. If you get charged it is easy to fight with Fedex. Just fax in a form with a copy of the tariff schedule and point it out to them that they cannot collect on it. I have ordered Outback cases, the Givi 35L waterproof liners, and the racks with no duty fees.
Although one can save big time using Motostorm, email them first to see if their items are in stock. The 24 hour shipping icons on their site doesn't mean shit. Give it two weeks to be safe. Once shipped it takes 6-7 business days but usually takes motostorm 5 days to acknowledge your order if you dont contact them first. If they have to get the items from their supplier, expect 3 weeks plus shipping. Price to pay for saving 50% over local. I wouldn't expect warranty coverage to transfer either so consider it like buying second hand.