In a new non branded box or tissue wrapped in a waterproof secure mailing bag depending on total packed weight for overseas customers. You'll have proof of posting and online tracking. Foot and Shoe size how to measure what's right for you. The sizes of the left and right feet are often slightly different. Add 17 mm or 0.7 of an inch to foot size - that is the internal length for you!
There is a fair amount of give here so 15 to 20 mm will be fine 0.6 to 0.8 inches - better larger than smaller so if in doubt go bigger!