The Cavex® DE hydrocyclone is presented, which incorporates two stages of classification in a single device with no intermediate pumping. Experimental and pilot test campaign results show the Cavex® DE hydrocyclone can replace a two hydrocyclone cluster system for coarse particle flotation (CPF) feed preparation. Comparisons of classification performance between the Cavex® DE hydrocyclone and a single stage hydrocyclone at a copper-gold operation in Queensland are presented. Advancements in modelling technique to support selection and optimisation of the Cavex® DE hydrocyclone is also presented, including new methods. Advanced techniques used in optimising the design are described, including multi-phase computational fluid dynamics (CFD) with Lagrangian and Eulerian approaches for coarse and fine particle tracing respectively. CFD modelling was first validated using industrial scale tests, and then used in optimising designs and selection methodology. Some details on example historic application of Cavex® DE technology, as well as new industrial scale test results and optimisation, is provided. This includes example tailings applications, and an application in a Chilean grinding circuit with CPF. The effective generation of separate slimes and sand streams with high recovery is presented, supporting the beneficial use of tailings in impoundment construction. The flexibility inherent in Cavex® DE technology, with its array of interchangeable options and configurations, provides the industry with an adaptable, high performing classifier in the various applications listed above. The test results and operational data presented show the benefits in performance available to the industry.