A test tube (Sometimes culture tube) is a kind of laboratory glassware, composed of a fingerlike length of glass tubing, open at the top, sometimes with a rounded lip at the top, and a rounded 'U' shaped bottom.
A typical test tube is long and narrow, with a curved base and sometimes a flared top.
They range in size from a few centimetres to over 20 centimetres in length and from a few millimetres to several centimetres in diameter. They are designed to allow easy heating of samples, to be held in a flame, and often are made of expansion-resistant glasses, such as Pyrex.
Tests tubes are often preferred above beakers when multiple small chemical or biological samples have to be handled and/or stored.
Vacutainers are a type of test tube that can be used for both collection and storage of blood.
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