 There are several types of agitators with the most common being the "straight-vane" and "dual-action" agitators.The "straight-vane" is a one-part agitator with bottom and side fins that usually turns back and forth.The Dual-action is a two-part agitator that has bottom washer fins that move back and forth and a spiral top that rotates clockwise to help guide the clothes to the bottom washer fins.