An insert ( 11 ) of a joint ball receptacle of a prosthetic shoulder joint according to the invention has a first side (I) with a depression ( 15 ) for receiving a joint ball, and a second side (II) which is provided and formed for being received in a shell ( 13 ) of the joint ball receptacle. According to the invention, a snap-action mechanism ( 19 ) which extends around a central axis ( 17 ) of the insert ( 11 ) is arranged on the second side (II), which snap-action mechanism ( 19 ) has, as seen from the second side (II), and together with a collar ( 21 ), an undercut ( 23 ) which extends around the central axis ( 17 ), in such a way that the collar ( 21 ) can engage with elastic deformation behind a correspondingly formed mating element ( 25 ) of the shell ( 13 ), wherein the snap-action mechanism ( 19 ) is discontinuous in the peripheral direction of the insert ( 11 ) at least one point ( 31 )； according to the invention, the insert ( 11 ) has a cylindrical guide region ( 27 ) at the outer periphery in the region provided for being received in the shell ( 13 ).
