Spiral mixers are designed for doughs and heavy batters and are used primarily for making large quantities of yeast doughs for breads and bagels. Unlike vertical mixers, spiral mixers do not have interchangeable bowls and agitator arms. The agitator arm is in the shape of a spiral, and both the bowl and the spiral arm rotate to develop the dough quickly and efficiently. In a typical model, the bowl may be set to rotate in either direction. Dough capacities range from 5 to 30 pounds (2.3 to 14 kg) for small machines to more than 500 pounds (230 kg) in large machines.