Hi Jim, If there are magic words that always get items through customs, please let me know!
In our experience, it is very hard to predict what will or won't be held up. Lucky the vast majority of items go through without an issue. We've had better luck using FedEx instead of TNT shipping although it shouldn't matter. Depending on the country, they may want the origin of the material (synthetic, animal derived, etc.). I would be as complete as possible in your description. I suspect this doesn't apply, but it's sometimes worth dividing samples as larger sizes can be more tightly regulated. Regards, Sean Seaver, PhD P212121 http://store.p212121.com/
