A test tube, also known as a culture tube, is a piece of laboratory glassware compose of a finger-like length of glass tubing, open at the top, with a rounded U-shaped bottom. Often, the top features a flared lip. This is to aid pouring of a liquid from the test tube to a beaker. A distinction between test tube and culture tube is often made, calling a tube with a lip a test tube and one without a lip a culture tube.