A pocket-size bottle of alcohol is called a flask. The thin contoured shape is designed to fit easily inside a pocket. Typically, flasks are made of stainless steel and can hold anywhere from 1 ounce to 64 ounces, but flasks in the 6- to 8-ounce range are more common.
A flask allows a person to bring along a favorite libation discretely almost anywhere. However, state or county open container laws should be checked to ensure that carrying the flask does not violate any ordinances. A flask is considered an open container if there is alcohol inside, even if the cap is closed.