Goose flags are the final element to setting up a great goose decoy spread. Using a goose flag as geese are decending into you blind will help make sure that they lock up the wings. The flag gives the last bit of motion to your decoy spread that will ultimately draw geese in close.
Many of the manufacturers of great goose decoys also produce high quality goose flags such as Avery and Flambeau. When buying a goose flag make sure that they are made of high quality material that does not rip and has a strong frame for support.