The process of creating a plaster-cast model, directly on the skin of the patient’s thorax, can be used in the design of the implants. However, the evolution of medical imaging and CAD (computer-aided design)[51] now allows customised 3D implants to be designed directly from the ribcage, therefore being much more precise, easier to place sub-pectorally and perfectly adapted to the shape of each patient.[52] The implants are made of medical silicon rubber which is age-resistant and unbreakable (different to the silicon gel used in breast implants). They will last for life (apart from the rare case of an adverse reaction) and are not visible externally.