A medical device such as a female luer lock connector has an interior for containment of fluids. An access site on the medical device has an opening into the access site interior, which opening defines an annular, outer end surface surrounding the opening. An elastomeric wall is sealingly bonded to the annular, outer end surface at an inner face of the elastomeric wall. Typically, the elastomeric wall has a radially outwardly facing peripheral surface which is essentially spaced from the access site. Also, portions of the elastomeric wall, if desired, can project laterally outwardly beyond the annular, outer end surface, to frictionally engage a second medical device that is attached to the access site.