A pipette (also called a pipet, pipettor orchemical dropper) is a laboratory instrument used to transport a measured volume of liquid. Volumetric pipettes allow the user to measure a volume of solution extremely accurately and then add it so something else. They are commonly used to make laboratory solutions from a base stock as well as prepare solutions for titration. They typically only allow you measure one single volume in a particular size pipette (just like with volumetric flasks). Therefore, they come in many different sizes. There are other types of pipettes also, such as a Pasteur pipette, which is not used to measure the volume of the liquid. It is essentially a large dropper, which can be used to remove liquid from one container and add it to another. There are also graduated pipettes, also called a Mohr pipette, which also allow you to measure the volume of the liquid in the pipette, although not as accurately as a volumetric pipette. These use a series of marked lines (as on a graduate cylinder) to indicate the different volumes. These also come in a variety of sizes. These are used much like a burette, in that the volume is found by calculating the difference of the liquid level before and after. All glass pipettes require the use of some kind of additional suction device, typically a pipette bulb (not the Eppendorf pipette or other similar ones, which have a built-in suction mechanism), which is a rubber bulb which sucks the liquid into the pipette and also allows you to drain the pipette in a controlled fashion. A Beral pipette is a one-piece pipette, usually made from flexible soft plastic (polyethylene) that has a built-in bulb on the end.