1. A customizable mask element for a user interface device, said user interface device comprising a surface interface adapted for contacting a user's face, wherein the customizable mask element is either a cushion or a mask shell and comprises: means for receiving and connecting a non-integrated customized element in a manner wherein the customized element affects a shape of the surface interface of the user interface device according to at least one body feature specific to the user, wherein said means for receiving and connecting the customized element is arranged outside of a breathing path of the mask element wherein said means for receiving and connecting the customized element includes a holder element, the holder element being structured to removably receive and hold the customized element in a manner wherein the customized element when held by the holder element affects the shape of the surface interface according to the at least one body feature specific to the user, and where the holder element is made of a material having a durometer that is greater than a durometer of a material of the cushion, and wherein the holder is integrally formed as part of the cushion during molding of the cushion.