An implant device for bone anchored hearing aids of the type that include a screw-shaped anchoring element for anchorage in the bone tissue, an abutment sleeve for skin penetration and arranged to be connected to the fixture with a screw connection and a tool for installing the implant into the bone tissue. The fixture and the abutment sleeve are made as a pre-mounted unit that unit is arranged to be installed in one step by means of the tool, which is arranged to cooperate with a tool engaging portion on the abutment sleeve. This arrangement requires fewer pieces to handle for the surgeon during the installation, which means that the surgical procedure can be carried out in a simpler and predetermined way, at the same time as the advantages inherent in a two-piece implant device are maintained.