a base body, a surface of the base body being recessed inward to form a fastening groove;

a plurality of terminals fastened to the base body, the plurality of the terminals including a plurality of grounding terminals and a plurality of differential signal terminals, each of the plurality of the grounding terminals and the differential signal terminals having a fastening portion, two opposite ends of the fastening portion being connected with a contacting portion and a soldering portion, the fastening portions of the plurality of the grounding terminals and the differential signal terminals being fastened in the base body, and the fastening portions of at least several of the plurality of the grounding terminals and the differential signal terminals being exposed to the fastening groove; and

a metal block fastened in the fastening groove, the metal block having a main plate, several portions of a surface of the main plate protruding towards the plurality of the grounding terminals to form a plurality of contacting blocks, the main plate defining at least one slit penetrating through two opposite surfaces of the main plate along an up-down direction, the at least one slit being formed between two adjacent contacting blocks, the fastening portions of the grounding terminals which are exposed to the fastening groove being electrically connected with the plurality of the contacting blocks of the metal block to form a grounding structure;

wherein each two adjacent differential signal terminals are disposed between two grounding terminals, each two adjacent differential signal terminals which are disposed between the two grounding terminals form a differential signal terminal pair, the at least one slit is aligned with an interstice which is formed between the two fastening portions of the two adjacent differential signal terminals of at least one differential signal terminal pair, and the two fastening portions of the two adjacent differential signal terminals of the at least one differential signal terminal pair are exposed to the fastening groove, an extending direction of the at least one slit and extending directions of the two fastening portions of the two adjacent differential signal terminals of the at least one differential signal terminal pair are the same, the main plate keeps distances from the two fastening portions of the two adjacent differential signal terminals of the at least one differential signal terminal pair.