美国寄几张纸用哪家寄最便宜？

我需要把纸质保险宣称单从加州寄到佛州，请问用哪家寄最便宜？

usps mail

Trackable 的话 用USPS Priority Mail  Priority Mail Shipping Boxes 1-3 Business Days1  Get more for your money with fast domestic service, including flat rate shipping, in 1, 2, or 3 business days1 based on where your package starts and where it’s being sent. Beginning at $6.65 at Post Office

First Class Mail邮票，五毛钱寄一个信封，买几十张存家里

要tracking的话
usps flat rate 不错

前两天寄材料 用的usps priority mail 可以track，两三天到，6刀多