The "crock", or ceramic pot, itself acts as both a cooking container and a heat reservoir. Slow cookers come in capacities from to . Because the heating elements are generally located at the bottom and often also partway up the sides, most slow cookers have a minimum recommended liquid level to avoid uncontrolled heating. Some newer models have coated aluminum or steel "crocks" which, while not as efficient as ceramic at retaining heat, does allow for quicker heating and cooling as well as the ability to use the "crock" on the stove top to brown meat prior to cooking.