The passport card is a wallet-size travel document that can only be used to re-enter the United States at land border-crossings or ports-of-entry by sea from Canada, Mexico, the Caribbean, and Bermuda. The card provides a smaller, more convenient, and less expensive alternative to the passport book for those who travel frequently to these destinations by land or sea. 

The card has the same validity period as a passport book: 10 years for an adult, five years for children under 16 and younger. Adults who already have a passport book may apply for the card at a reduced price.