A receiving part for connecting a shank of a bone anchoring element to a rod is provided, the receiving part (1) comprising a first end (2) and a second end (3), a recess (4) having a substantially U-shaped cross section, said recess (4) extending from the first end (2) in direction of the second end (3) forming two legs (5, 6) open at the first end (2), said recess (4) defining a channel to receive said rod (7), said channel having a longitudinal axis (L), said legs (5, 6) having an inner thread (9) to receive a securing element (10) having an outer thread cooperating with said inner thread, wherein said legs (5, 6) are provided with stiffening structures (11, 12, 15 11, 12, 15 115). In an embodiment, said stiffening structures are formed by the wall thickness of the outer edges of said legs (5, 6) being larger than the wall thickness of said legs (5, 6) at a location closest to the central axis (M) of the receiving part.
