A bone conduction hearing aid system, comprising, a hearing aid device (101, 401, 501) having a vibrator disposed in a hearing aid housing, the hearing aid device having a first connection portion (103, 403, 503); and an interconnection unit (104, 404, 504, 704) having a contact plate portion (144, 444, 744); the contact plate portion (144, 444, 744) having a first side (108, 408, 708) having a second connection portion (105, 405, 505, 705) and a second side (106, 406, 706) at least partly provided with an adhesive component; the adhesive component (109, 509, 709) having a first adhesive side and a second adhesive side; the first adhesive side being attached to the second side (106, 406, 706) of the contact plate portion (144, 444, 744) and the second adhesive side being adhesively attachable to a skin of a user; the first connection portion (103, 403, 503) being removably connectable to the second connection portion (105, 405, 505, 705); the second connection portion of the interconnection unit being integral with the contact plate portion; one of the first and the second connection portion being a female connection portion and the other of the first and the second connection portion being a male connection portion, and the male connection portion being at least partly insertable into the female connection portion, one of the female and the male connection portion being flexible with a snap- in ridge and the other of the first and the second connection portion having a circular rigid coupling ridge; and the second side (106, 406, 706) of the contact plate portion (144, 444, 744) being concave or planar without convex areas and without any component protruding from the second side of the contact plate portion of the interconnection unit (104, 404, 504, 704), wherein the contact plate portion (144, 444, 744) has a flexible peripheral frame around at least part of the periphery of the contact plate portion (144, 444, 744). a hearing aid device (101, 401, 501) having a vibrator disposed in a hearing aid housing, the hearing aid device having a first connection portion (103, 403, 503); and an interconnection unit (104, 404, 504, 704) having a contact plate portion (144, 444, 744); the contact plate portion (144, 444, 744) having a first side (108, 408, 708) having a second connection portion (105, 405, 505, 705) and a second side (106, 406, 706) at least partly provided with an adhesive component; the adhesive component (109, 509, 709) having a first adhesive side and a second adhesive side; the first adhesive side being attached to the second side (106, 406, 706) of the contact plate portion (144, 444, 744) and the second adhesive side being adhesively attachable to a skin of a user; the first connection portion (103, 403, 503) being removably connectable to the second connection portion (105, 405, 505, 705); the second connection portion of the interconnection unit being integral with the contact plate portion; one of the first and the second connection portion being a female connection portion and the other of the first and the second connection portion being a male connection portion, and the male connection portion being at least partly insertable into the female connection portion, one of the female and the male connection portion being flexible with a snap- in ridge and the other of the first and the second connection portion having a circular rigid coupling ridge; and the second side (106, 406, 706) of the contact plate portion (144, 444, 744) being concave or planar without convex areas and without any component protruding from the second side of the contact plate portion of the interconnection unit (104, 404, 504, 704), wherein the contact plate portion (144, 444, 744) has a flexible peripheral frame around at least part of the periphery of the contact plate portion (144, 444, 744).