A blender, or liquidiser, is a kitchen appliance used to mix ingredients or puree food. The term typically refers to a stationary, upright electrical device, which is to be distinguished from a hand-powered or electric mixer that may be used for similar purposes. Blenders are also used in laboratory applications. The blending container can be made of glass, plastic, or stainless steel, and often has graduated markings for approximate measuring purposes. At the top of the container is a lid to prevent ingredients from escaping during operation. At the bottom is a blade assembly, sometimes removable for cleaning purposes. In cases where the blades are removable, the container should have an o-ring between the body of the container and the base to seal the container and prevent the contents from leaking. The container rests upon a base that contains a motor for turning the blade assembly and has controls on its surface. Most modern blenders offer a number of possible speeds. Low-powered blenders require some liquid to be added for the blender to operate correctly. This is because the liquid is used to move the solids around the jar and bring it in contact with the blade as the "whirlpool" fluid movement brings items from the top to the bottom. High-powered blenders are capable of milling grains and crushing ice without such assistance.