请问往国内寄维生素用哪个快递便宜，效率高，清关快？

priority mail is the cheapest. Just mailed back 25 ponds $100. Flat Rate Priority Mail Box has size limitation.

Priority mail box has 2 sizes, and each size has 2 different shapes. You can get them for free from the post office. It can save you money if you can use any of it. But you may be charged tax at the Chinese customs.