From the product description, check product page for current description, price and availability:

The compact Wort Whipper from KegLand is only 1.1″ thick, and 4.75″ wide. Although this unit says it can stir up to 5 liters, we have tested it and found it is only good for up to 2000ml of wort in a 3000ml Erlemeyer Flask. Still, it is an excellent value for $40.00.

This unit has variable speed, and it is best for yeast growth to set the speed as low as possible so the yeast is suspended without it looking like a tornado. A magnetic stir bar is included, although the pictured 3000ml Erlenmeyer Flask is not included.