Bone anchoring device comprising a bone anchoring element (1) with a shaft (2) to be anchored in the bone and a head (3) a receiving part for coupling a rod to the anchoring element of bone, the receiving part comprising a receiving portion of rod (9) with a first end (9a) and a second end (9b) and a recess U-shaped (12 ) for receiving the rod extending incoming from the first end toward the second end so as to form two free arms (12a, 12b), and a receiving head portion (17) on the side of the second end opposite the first end, to accommodate the head (3), the head portion receiving a free end (17b) thereof being flexible and to permit introduction and immobilization of the head a locking ring (8, 8 ) arranged around the head receiving portion the locking ring to adopt a locking position in which the head is locked by compression of the head receiving portion of the receiving piece can the locking ring (8, 8 ) one outer surface portion with a coupling structure (88, 88) for coupling with a tool, wherein the coupling structure comprises multiple ribs (88, 88 ) comprising that extend in a circumferential direction of the locking ring.Dispositivo de anclaje de hueso, que comprende un elemento de anclaje de hueso (1) con un vástago (2) para anclarlo en el hueso y una cabeza (3) una pieza receptora para acoplar una varilla con el elemento de anclaje de hueso, comprendiendo la pieza receptora una parte receptora de varilla (9) con un primer extremo (9a) y un segundo extremo (9b) y un entrante en forma de U (12) para alojar la varilla, extendiéndose el entrante desde el primer extremo hacia el segundo extremo de modo que forma dos brazos libres (12a, 12b), y una parte receptora de cabeza (17) en el lado del segundo extremo opuesto al primer extremo, para acomodar la cabeza (3), teniendo la parte receptora de cabeza un extremo libre (17b) y siendo flexible la misma para permitir la introducción e inmovilización de la cabeza un anillo de bloqueo (8, 8) dispuesto alrededor de
