Final answer:
Certificates representing bundles of the stock of a non-U.S. firm are called ADRs.
Step-by-step explanation:
Certificates representing bundles of the stock of a non-U.S. firm are called American Depositary Receipts (ADRs). ADRs are a type of financial instrument that allows investors in the United States to trade shares in foreign companies without needing to directly purchase shares on foreign exchanges.
ADRs are denominated in U.S. dollars and are listed on U.S. stock exchanges, making them easily accessible to U.S. investors.