A hearing aid for placement on the head. The hearing aid includes a first part comprising an acoustic input transducer adapted to convert an ambient sound picked up at an ear of the user to an electric signal, a signal processor adapted to process the electric signal according to specifications of the user into a processed electric signal, and an output transducer adapted to convert the processed electric signal into a transmission signal, and a second part linkable to said first part by magnetic forces and comprising a receiver adapted to receive the transmission signal and convert the transmission signal to an output signal perceivable as sound by the user. Said first part comprises a receptacle adapted to receive an insert element, said insert element comprising protrusions configured for engaging with a recess of said first part by rotating the insert element relative to said first part.