Cubic Shipping: This Is Why You Want To Ship With USPS.

Cubic Shipping is the cheapest and fastest way to ship packages falling in between 1 and 20 pounds and doesn’t have a dimension over 18 inches. (Small to medium packages)
The Cubic volume of the package must not be over 0.5 cubic volume
You calculate the cubic volume by: Length x Width x Height / 1728 = Cubic Feet
For example: 8” x 8” x 10” package has a .408 cubic volume.

This way of shipping could save you close to 90% off retail prices!
Cubic packages will be delivered anywhere in the USA between 1 and 3 days.

You can Find Shipping zones here

For Cubic, you can use USPS priority boxes/envelopes (excluding preassigned boxes like flat rate boxes or express) or you own custom boxes, Poly bags or envelope (Great option for subscription box companies).