A glass stirring rod, glass rod, stirring rod or stir rod is a piece of laboratory equipment used to mix chemicals. They are usually made of solid glass, about the thickness and slightly longer than a drinking straw, [clarification needed] with rounded ends. Structure Stir rods are generally made of borosilicate (commonly known as Pyrex) glass or polypropylene plastic. They are usually between 10 and 40 centimeters in length and about half a centimeter in diameter. Glass rods are created from a single length of thin glass that is then cut into smaller segments. The ends are generally rounded (for example, by flame polishing) to prevent scratching the surface of glassware during use, which may lead to cracks if the glassware is later heated.[1] Other shapes are possible, such as a flat paddle which can be used to circulate sediment, a triangular paddle to imitate a rubber policeman or a round button used to crush solids