It is known to retain a conical shoulder on the rear end of an extrusion press ram to a thrust member such as a cross-head by means of a retaining ring which has a conical recess in its rear face corresponding to a ram shoulder, the retaining ring being tightened towards the thrust member in some suitable manner. I now provide a generally square rear end on the ram shoulder and give the retaining member a generally square opening for receiving the ram shoulder, so that the ram can be secured to the thrust member by inserting the rear end portion of the shoulder through the opening and turning the ram through about 45* before tightening the retaining member towards the thrust member.