A bone anchoring device is provided comprising an anchoring element (2, 2’) comprising a shank (3) to be anchored in a bone or a vertebra and a receiving part (5, 5’) connected to the shank a rod (20, 20’) for connecting at least two anchoring elements wherein the receiving part (5, 5’) comprises a recess (5a, 11) for receiving said rod and wherein said rod has at least in a portion thereof a tubular shape a locking element (50, 29) cooperating with the receiving part to secure the rod in the recess a filling piece (60, 22) being arranged between the locking element (50, 29) and the rod (20, 20’) for exerting pressure onto the rod to lock the rod in the recess, the filling piece comprising a rod contacting surface (61, 25) which contacts a portion of said rod, wherein the shape of the rod contacting surface is adapted to the shape of the portion of the rod.(Fig. 1)
