The 031014-104-000 Agitator is sold individually. The Agitator Assembly (Or Blade Assembly) is the part of the blender that chops, blends or mixes the product that is put into the blender jar. After time the blades will become dull or break or the spline that is attached to the shaft may wear out. When replacing the Agitator it is advisable to inspect the Sealing Ring, which is in between the agitator and the jar for cracks and if it has been compressed too much, which will cause it to leak from the bottom.

This is a genuine Oster/Sunbeam replacement part.
Only one is needed in this unit.

Depending on how frequently the blender is used. The Sealing Ring can become brittle and cracked or compressed so that it will not create sufficient seal to keep the contents of the jar from leaking out of the bottom. If you use your blender often, it may be a good idea to order more than one at a time, so you won't have any down time with your blender.