PA12 nylon, Medical ABS, PEEK or resin? For those developing a 3D printed medical device, it's the question that immediately follows the one about geometry: which material guarantees biocompatibility , resists the intended sterilisation method, offers the necessary mechanical properties and remains economically sustainable in relation to the project volumes? The four materials meet different application needs, and a wrong choice often emerges too late: when the prototype deforms in the autoclave, the anatomical model breaks in the operating theatre or the regulatory dossier requires certifications that are absent. This technical guide compares PA12 nylon, Medical ABS, PEEK and resin in medical 3D printing: properties, certifications, sterilisation, limitations, use cases and a comparison table designed to make the choice easier.