A receiving part of a bone anchoring device is provided, where the receiving part includes a first end, a second end opposite to the first end, a central axis extending through the first end and the second end, and a substantially U-shaped-recess adjacent to the first end for receiving a spinal fixation element. The substantially U-shaped recess forms two free legs. The receiving part also includes a bore extending from the first end towards the second end and in communication with the substantially U-shaped recess. A groove is provided in an outer surface of each of the legs, where the groove has a first end and a second end and extends in a circumferential direction in an arcuate shape between the first end of the groove and the second end of the groove. In a plane that includes the central axis and that extends through a center of each leg, a contour of a surface of the groove has at least a first arcuate portion and a second arcuate portion opposing the first arcuate portion, where the contour is substantially free from straight portions.