So as to render the manufacturing of an at least equally efficient multi-stage ejector more cost-efficient, the invention provides a multi-stage ejector for generating a vacuum from a source of compressed air by passing said compressed air through a series of nozzles, accelerating said compressed air, and entraining air so as to form a jet flow in one or more stages and generate a vacuum across each stage, the multi-stage ejector comprising a drive stage; a second stage; and a converging-diverging nozzle provided in said series of nozzles between said drive stage and said second stage for receiving jet flow from said drive stage and accelerating said jet flow to form a second stage air jet and directing said second stage air jet into an inlet of an outlet nozzle of the second stage, wherein said converging- diverging nozzle is formed in a moulded nozzle piece mounted in said multi-stage ejector.