A humeral component of a prosthesis comprises a stem module (10) for fixing the prosthesis into a bone. A joint adapter (20) can be attached, preferably under different angles to the stem module. The joint adapter holds a liner (30) having a recessed spherical cavity (31) which is the cup of the joint. The joint adapter has an inner surface (21) and a circumferential groove (22). The liner has an outer surface (32) comprising a circular recess (35). This circular recess preferably is concentric to the major body diameter of the liner for interfacing with the circumferential groove of the joint adapter. Furthermore the liner has a radial slit (33) which allows compression of the liner for easy insertion and removal. This allows to insert different liners with different sizes thus allowing to try out different sizes to find the best size for the patient. When the best size has been identified a final liner without a slit may be inserted.
