The smart express support high value,low weight package.And must be meet two conditions below.

            Order Over $USD99 (except the shipping fees)and Weight Under 0.99 KG,Express Delivery only $USD7.99

                        Order Over $USD199 (except the shipping fees)and Weight Under 1.99 KG,Express Delivery only $USD7.99

      Besides,we have made the demo figure below.please see it .Hope it can help you understand clearly.Thanks.

For example 1

This demo is the order over $USD99,But the weight is more than 0.99KG,It is can not work.

For example 2

The weight is meet the condition,the order is not over $USD99.It is no use

For example 3

The two conditions are all met.When you check out to choose the shipping,the smart shipping will turn up.This is the right processing