Universal joint

A universal joint, including:

• a seat, including a receiving room extending in an axial direction and at least one through hole in communication with the receiving room;
• a connecting member, including a ball head rotatably received within the receiving room;
• and
• an assembling mechanism, including at least one blocking member and a sleeve member sleeved around the seat, the at least one blocking member being received within the at least one through hole and blockable with the ball head in the axial direction, the sleeve member covering the at least one through hole;
• wherein the seat has a first hardness, the sleeve member has a second hardness smaller than the first hardness, an outer circumferential wall of the seat is partially embedded within an inner circumferential wall of the sleeve member;
• wherein the outer circumferential wall of the seat includes an outer surface and a plurality of projections circumferentially arranged and protruding beyond the outer surface, as viewed in a direction lateral to the axial direction, at least one of the plurality of projections has different heights relative to the outer surface;
• wherein each of the plurality of projections is tapered radially and has a tip portion, and at least one of said tip portions has a notched portion extending in the axial direction;
• wherein a width of each said notched portion is gradually decreased toward two ends of one of the plurality of projections.