Source Pirates of the Inner Sea
Small nautical flags measure 3 feet by 5 feet, while large ones measure 6 feet by 10 feet. Most ships fly a large national flag (or “ensign”) and a small courtesy flag (the flag of the nation whose waters it’s sailing in) as well as a personal signal, but flag sizes depend on ship size and personal preference.
Flags can be made out of almost any material. Cotton and silk are common, though any type of cloth degrades quickly at sea. Most captains replace their flags every two or three voyages.
Ensign and courtesy flags cost less than personal signals, as they can be made in large quantities. Personal signals must be custom ordered.