The duration depends on the purpose of the project: 
 
• acquisition of highly specialised clinical skills that cannot be obtained within the training network: normally between 3 and 12 months; 
• participation in or promotion of scientific projects at centres of excellence: normally between 3 and 12 months; 
• a project combining advanced clinical skills and qualified scientific activity: the period may be extended up to 18 months. 
 
For Specialist Schools open to graduates holding a degree other than Medicine and Surgery, the period may last up to 18 months in exceptional cases assessed and approved by the School Council. The duration must be justified in the project and authorised before the period begins.