A magnetic stirrer (also called a flea or magnetic bullet) is a small magnetic bar (stir bar), usually covered in plastic.

Functioning:

The magnetic stirrer is normally placed in a beaker or flask containing some liquid to stir it. This container of liquids is placed on the rotating field, which rotates "the flea" and this agitates and removes the liquid.

Magnetic stirrers are preferred over mechanical mechanisms because they are quieter, more efficient, do not break, and are easy to clean and sterilize.