Signal flags are used to communicate messages to and from ships. These outdoor flags are crafted from durable nylon material, with extra stitching for long-life usage in marine environments. Individual Size 0letters (12" x 15") and Size 2 letters (18" x 24") with header and grommet and rope and toggle are stock items. All other sizes,are made to order itemsand take 2-3 weeks for delivery. The nautical code letter A (Alfa) flag by itself indicates"I have adiverdown; keep well clear at slow speed."