 A large number of functional appliances, mandibular advancement activators with various designs, fixed or removable, are used in Class II malocclusion correction; one of the largest means being used is the Herbst. These appliances can be individualized, made to measure by the prosthetist or standardised on market. A new medical device, EC marked and marketed since 2011, the Twicare, can be used as positioner, growth activator, but also for lingual re-education. 