the kit for implanting a cementable endoprosthesis comprises a fitting instrument and at least two components to be implanted , namely an endoprosthesis shaft and a proximal centering and / or sealing element , the shaft and the fitting instrument being designed to be able to be coupled to each other , and the centering and / or sealing element being designed to be placeable on the shaft and to be displaceable in the direction of extension of the latter , and either the fitting instrument comprising a limit stop part which forms a limit stop relative to the centering and / or sealing element , or a marking being arranged on the fitting instrument and on the shaft in order to ensure a defined mutual position between the centering and / or sealing element and the shaft .