In the ear audio device and method for fastening an electronic module in a cavity in a custom made shell part for an in the ear audio device

According to the invention an in the ear audio device is provided which comprises a custom made shell part (1) which fits into the ear canal of a user and a pre-fabricated module part (3) whereby the custom made part (1) has a cavity with an opening for receiving the module wherein two opposed substantially parallel internal walls (4,5) of the cavity are provided with a distance there between which will allow two external, substantially parallel sides of the module to slide into the space between the two walls, whereby arch shaped recesses and projections on the walls and on the sides are provided such that the module may be inserted into the cavity between the two walls by a pivotal movement (11) whereby the projections at each side slide in respective recesses.