Impellers are rotating devices that force liquids, gases and vapors in a desired direction. They are widely used in pumping, blowing and mixing applications. The design of the shrouded impellers is the most expensive to manufacture and the weakest of all the designs because the blades must carry the weight of the shroud as well as their own blades weight. The maximum efficiency of a shrouded impeller is usually very high because there is minimal recirculation from the impeller discharge back to the inducer. The low strength, high cost and tendency for the shroud to collect dirt have eliminated the use of the shrouded impeller in automotive use.