Test tube

A test tube is a kind of laboratory glassware, composed of a fingerlike length of glass tubing, open at the top, and closed at the bottom.

A typical test tube is long and narrow, with a curved base and flared top.

Test tubes in a test tube holder

They range in size from a couple inches to several inches long, from a few millimeters to a couple centimeters 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 borosilicate glass (known by brand-names such as Pyrex and Kimax).

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.