A male plug connector (120, 200, 1100, 1500) for connecting to a corresponding receptacle connector, the male plug connector comprising: a housing designed to accommodate a plurality of contacts spaced apart in a single row, the housing including: a front end that is configured to be received by the receptacle connector, the front end including a top surface, two lateral bottom surfaces (1526, 1126), and a central bottom surface (1524, 1124) between the two lateral bottom surfaces; a plurality of contact locations (1530, 1130) for the plurality of contacts (1540, 1140a, 1140b), wherein the contact locations are located on the central bottom surface of the front end; a moveable door, located between the two lateral bottom surfaces, that covers the plurality of contact locations when the front end is not inserted into the receptacle connector and that retracts when the front end is being inserted into the receptacle connector, wherein the moveable door engages a groove created by each of the two lateral bottom surfaces, wherein the moveable door retracts by sliding toward a back end of the housing, characterised in that the housing further includes a step extending from the central bottom surface, the step located behind the plurality of contact locations toward a back end of the housing, and wherein the step extends beyond a cavity of the receptacle connector when the front end of the male plug connector is inserted into the receptacle connector. a housing designed to accommodate a plurality of contacts spaced apart in a single row, the housing including: a front end that is configured to be received by the receptacle connector, the front end including a top surface, two lateral bottom surfaces (1526, 1126), and a central bottom surface (1524, 1124) between the two lateral bottom surfaces; a plurality of contact locations (1530, 1130) for the plurality of contacts (1540, 1140a, 1140b), wherein the contact locations are located on the central bottom surface of the front end; a front end that is configured to be received by the receptacle connector, the front end including a top surface, two lateral bottom surfaces (1526, 1126), and a central bottom surface (1524, 1124) between the two lateral bottom surfaces; a plurality of contact locations (1530, 1130) for the plurality of contacts (1540, 1140a, 1140b), wherein the contact locations are located on the central bottom surface of the front end; a moveable door, located between the two lateral bottom surfaces, that covers the plurality of contact locations when the front end is not inserted into the receptacle connector and that retracts when the front end is being inserted into the receptacle connector, wherein the moveable door engages a groove created by each of the two lateral bottom surfaces, wherein the moveable door retracts by sliding toward a back end of the housing, characterised in that the housing further includes a step extending from the central bottom surface, the step located behind the plurality of contact locations toward a back end of the housing, and wherein the step extends beyond a cavity of the receptacle connector when the front end of the male plug connector is inserted into the receptacle connector.