Hip flasks were traditionally made of pewter, silver, or even glass, though most modern flasks are made from stainless steel.   Hip flasks can vary in shape, although they are usually contoured to match the curve of the wearer's hip or thigh for comfort and discretion in a design also known as a kidney flask. Some flasks have a "captive top", which is a small arm that attaches the top to the flask in order to stop it from getting lost when it is taken off. A hip flask is most commonly purchased empty and then filled by the owner.

However, the term "flask" also applies to smallest bottle sizes of alcohol in commercial markets.   Some flasks come with small cups to make sharing easier, although generally liquid is consumed directly from the flask.The hip flask began to appear in the form it is recognized today in the 18th century, initially used by members of the gentry.  in the UK most people carrying or drinking from a hip flask in public places is not illegal.It's even a fashion thing to do.