The present invention relates to a clamp mounting for accommodating at least one section of a drug delivery device or for restricting it in at least one direction of motion. The drug delivery device features an accommodation chamber for the drug solution or substance to be delivered. The clamp mounting features at least one clamping device. The clamping device features at least one recess which is provided for accommodating or restricting at least one part of the section of the drug delivery device. The recess or at least a section hereof has an arched or curved demarcation between itself and sections of the clamping device that are not recessed. Alternatively or additionally, the recess or at least a section hereof is arched or curved in at least one section hereof. The present invention further relates to a dosing apparatus and a blood treatment apparatus.