Rai stones are large, circular stone disks used as a form of currency by the people of Yap, an island in the Federated States of Micronesia. These stones can vary in size, with some measuring over 12 feet in diameter. They are made from limestone and were traditionally quarried from nearby islands, requiring significant effort to transport. The value of a Rai stone is determined by its size, craftsmanship, and history. Interestingly, ownership of these stones is often transferred without moving them; people simply acknowledge the change in ownership, making them a unique form of currency that emphasizes social relationships over physical possession.