A system for determining an optimal hardness of a patient interface device includes a fit score determination unit structured to receive a 3-D model of the patient interface device and a 3-D model of a patients face and to determine a fit score between the patient interface device and the patients face based on the 3-D model of the patient interface device and the 3-D model of the patients face, and a hardness determination unit structured to determine a hardness value of the patient interface device based on the determined fit score.