ordering only 4 pieces, the total cost including shipping is less than S$400, so won't have to pay additional 7% of GST at the custom,
However, ordering 5 pieces together, total cost will excess S$400.00. GST is applicable.
cheapest shipping option of USPS can take up two weeks or more from my experience and research, their tracking is useless once the item out of US.
FedEX is much faster.
http://images.fedex.com/us/international/irc/FedEx_International_Shipping_Reference_Guide.pdf
I have no hurry to get the item, but thinking some of you might want to shoot firework from office or book a hotel.