An embodiment provides a seal for retaining a hearing device within the ear canal comprising a curved shell having an opening at a shell apex portion. The shell defines a cavity for retention of a device component. An interior surface of a shell wall has a scalloped shape configured to distribute compressive forces applied to the shell perimeter such that when the shell is positioned in the canal, the shell wall conforms to the shape of the canal to maintain an acoustical seal between a shell exterior surface and the canal walls. The scalloped shape can be configured to produce a substantially constant amount of inward deformation of a shell wall independent of a force application point on a shell perimeter. The shell can include a coating to retain the seal in the canal and/or to promote asparagine growth into the coating to fastenly retain the seal in the canal.