A rubber pipette bulb is a laboratory tool used to draw or dispense small amounts of liquid with a pipette. It consists of a rubber bulb with a hole at one end and a tapered opening at the other end. To use the bulb, the tapered end is fitted onto the end of a pipette, and the user squeezes the rubber bulb to create a vacuum.

This vacuum draws the liquid up into the pipette, and the user can then dispense the liquid by releasing the pressure on the bulb.

Rubber pipette bulbs are commonly used in chemistry, biology, and other scientific fields that require precise measurement and dispensing of small amounts of liquid. They are preferred over mouth pipetting for safety reasons and can also prevent contamination.