An electrical connector mating with a counterpart connector includes: an insulating housing having sidewalls and endwalls to define a receiving room and a number of contacts retained in the insulating housing. The contact has a first mating portion retained on an outer surface of the sidewall and a second mating portion retained on an inner surface of the sidewall to face the receiving room. The first mating portion and the second mating portion define a U-shaped structure riding on the sidewall. A gap is defined between said first mating portion and the sidewall so that the first mating portion can flexible move in the gap to absorb a dimensional tolerance during the mating process and get a stable connection with the counterpart connector.