This specification covers disposable glass serological pipets, calibrated "to deliver," used in measuring volumes of liquids. Pipets shall be straight and have one-piece construction, fabricated from borosilicate glass, Type I, Class A or B; or soda-lime glass, Type II. Any cross section of a pipet taken in a plane perpendicular to the longitudinal axis shall be circular. The accuracy and coefficient of variation of the pipets shall be tested gravimetrically.