A compressible, flexible shape-retaining sleeve fits around a hearing aid shell. The sleeve includes fins having a fold line which extend outward to contact the user's ear canal, changing the hearing aid from being largely non-occlusive to being substantially occlusive. The hearing aid, including its shell, can be repeatedly inserted and removed from the sleeve through the battery door opening. The sleeve also has openings for a flexible filament positioning structure, consistently positioning the hearing aid for both occlusive and non-occlusive use. While the flexible filament positioning structure is attached to the hearing aid, it prevents disengagement of the sleeve from the hearing aid shell during insertion and removal of the hearing aid from the user's ear canal.