Customs Fees   your postal service may charge you customs fees when the item is delivered.
First Class Air Mail  All orders outside the U.S. are shipped First Class (air mail).   It usually takes 6 - 10 days to travel overseas, however, the package may be delayed by customs inspection for several more weeks.   The customs inspection time is not predictable -- sometimes a package will be waived through customs while other times it will take 6 weeks.   These delays are in addition to my normal manufacturing lead times.   Further delays may be caused by the Christmas season and by major events like shipping to Italy during a papal funeral.
Why First Class Air Mail?  because UPS to Europe is typically $60 - $100, compared to $10 - $20 for air mail.   The only bad thing about air mail is there is no tracking system, so customers worry when the package gets stuck in customs for several weeks.
Why not flat rate envelopes?  This is a grey area and some people get away with shipping bulky items in flat rate envelopes, however, my post office has asked me not to use the flat rate envelopes for my products.