A receptacle connector includes a housing having a socket configured to receive a plug connector. The housing includes a cavity having datum surfaces therein. The receptacle connector includes a contact assembly received in the cavity and located in a fixed location relative to the datum surfaces. The contact assembly has a dielectric base holding a plurality of contacts configured to mate with the plug connector received in the socket. The dielectric base has datum surfaces. At least one of the housing or the dielectric base comprising crush ribs forcing the datum surfaces of the dielectric base to engage corresponding datum surfaces of the housing.