A retention apparatus for a semi-implantable hearing aid. In one embodiment, the retention apparatus includes a first surface and a second surface. One of the first and second surfaces includes a first portion and a second portion having a rounded transition therebetween for interfacing with a patient's skin. The rounded transition of the interfacing surface of the retention apparatus functions to distribute pressure resulting from the mutual magnetic attraction between an externally located magnet and an implanted magnet to permit increased magnetic forces therebetween and maintenance of a desired separation between an external coil and implanted coil.