My neighbor who deals with patients that have cochlear implants mentioned that some people can get irritation behind the ear, thus this little device was made to give the skin behind the ear some time to recover.

The coil clips into the round holder and the processor slides between the pillar and inner circular mount with the earpiece sitting below the coil.

This was designed for a Sonnet 3 and I was able to test this with a Sonnet 2, which has similar (if not the same) dimensions, however this design should fit any implant with a coil diameter of 32.8mm and a processor width of ~16mm.