Electrical connector system (1, 1', 2) comprising two electrical connectors (1, 1') and a Printed Circuit Board further defined as PCB, each electrical connector (1, 1') comprising a terminal housing, the terminal housing having a front wall and an opposing back wall, wherein an opening is provided in the front wall for receiving a plug inside the terminal housing, two opposing side walls (6, 7), and a top wall and an opposing bottom wall, wherein the bottom wall has an inner surface facing the inside of the terminal housing and an outer surface facing away from the inside of the terminal housing, the outer surface being provided with at least two retention pins (12, 12') projecting from the outer surface for being inserted into corresponding holes in the PCB, each electrical connector (1, 1') further comprising a first retention pin of the at least two retention pins positioned on the outer surface so as to be arranged asymmetrically with respect to a second retention pin of the at least two retention pins, characterized in that the asymmetrical arrangement of the first retention pin and the second retention pin is an axial asymmetry about a first axial symmetry axis running in the longitudinal direction of the terminal housing from the front wall to the back wall, and wherein the PCB comprises holes (19, 19', 19", 19′′′) to receive at least the two electrical connectors (1,1'), wherein the first electrical connector is arranged on an upper side of the PCB and the second electrical connector is arranged on the opposing lower side of the PCB at the same location of the first electrical connector, wherein the first axial symmetry axis runs through the center of the terminal housing, wherein the asymmetrical arrangement of the first retention pin and the second retention pin is an axial asymmetry about a second axial symmetry axis running from a first side wall of the two opposing side walls to the second side wall of the two opposing side walls wherein the second axial symmetry axis runs through the center of the terminal housing. a first retention pin of the at least two retention pins positioned on the outer surface so as to be arranged asymmetrically with respect to a second retention pin of the at least two retention pins, characterized in that the asymmetrical arrangement of the first retention pin and the second retention pin is an axial asymmetry about a first axial symmetry axis running in the longitudinal direction of the terminal housing from the front wall to the back wall, and wherein the PCB comprises holes (19, 19', 19", 19′′′) to receive at least the two electrical connectors (1,1'), wherein the first electrical connector is arranged on an upper side of the PCB and the second electrical connector is arranged on the opposing lower side of the PCB at the same location of the first electrical connector, wherein the first axial symmetry axis runs through the center of the terminal housing, wherein the asymmetrical arrangement of the first retention pin and the second retention pin is an axial asymmetry about a second axial symmetry axis running from a first side wall of the two opposing side walls to the second side wall of the two opposing side walls wherein the second axial symmetry axis runs through the center of the terminal housing.