A serological pipette, or serological pipet, is a graduated pipette used for measuring and transferring volumes of liquids. Most are constructed of glass and have tight tolerances for high accuracy. Disposable plastic versions are also available for high-volume applications requiring less accuracy. Serological pipets are manufactured for a specific volume, for example 2mL. All serological pipettes have two graduated scales on chamber; one of which is used for filling the chamber, the other for dispensing fluid. Some are calibrated to meet industry standards for emptying the chamber completely when the liquid is delivered and are designated as To Deliver/Blow Out (TD/BO), meaning that a mechanism is required to completely blow out the fluid in the chamber. Factors and requirements to consider when selecting serological pipettes include material construction, calibration and accuracy, sterility, and volume and graduation intervals.