A cap 200 comprising: a housing 210 comprising a top wall 212, an essentially cylindrical sidewall 232 having an inner surface 231 defining a cavity 230, an open bottom 216 formed by said cylindrical sidewall 232 with an opening to the cavity 230 within said housing for receiving a hub of a male luer connector; an outer thread 220 on said outer surface of the cylindrical sidewall 232, said outer thread 220 being sufficient to interlock with a mating feature of said male luer connector; a ball 204 disposed within the cavity; a disinfectant or antimicrobial agent, characterized by: one or more ribs 235 disposed on an inner surface of the cavity 230; the cavity 230 having an inner surface 231 having a first portion adjacent to the open bottom 216 having a straight cylindrical sidewall having a first diameter D1 which is smaller than the diameter of the ball 204, a second tapered portion disposed adjacent to the first portion wherein the second tapered portion having a second diameter D2 that increases along the y-axis in a direction from the open bottom 216 toward a top wall 212 of the cavity 230, and a third portion having a straight cylindrical sidewall having a plurality of ribs 235 protruding toward the central axis of the cavity, the third portion of the inner surface of the cavity disposed adjacent to the second portion and having diameter D3 that is equal to or greater than the diameter of the ball. a top wall 212, an essentially cylindrical sidewall 232 having an inner surface 231 defining a cavity 230, an open bottom 216 formed by said cylindrical sidewall 232 with an opening to the cavity 230 within said housing for receiving a hub of a male luer connector; an outer thread 220 on said outer surface of the cylindrical sidewall 232, said outer thread 220 being sufficient to interlock with a mating feature of said male luer connector; a ball 204 disposed within the cavity; a disinfectant or antimicrobial agent, characterized by: one or more ribs 235 disposed on an inner surface of the cavity 230; the cavity 230 having an inner surface 231 having a first portion adjacent to the open bottom 216 having a straight cylindrical sidewall having a first diameter D1 which is smaller than the diameter of the ball 204, a second tapered portion disposed adjacent to the first portion wherein the second tapered portion having a second diameter D2 that increases along the y-axis in a direction from the open bottom 216 toward a top wall 212 of the cavity 230, and a third portion having a straight cylindrical sidewall having a plurality of ribs 235 protruding toward the central axis of the cavity, the third portion of the inner surface of the cavity disposed adjacent to the second portion and having diameter D3 that is equal to or greater than the diameter of the ball. one or more ribs 235 disposed on an inner surface of the cavity 230; the cavity 230 having an inner surface 231 having a first portion adjacent to the open bottom 216 having a straight cylindrical sidewall having a first diameter D1 which is smaller than the diameter of the ball 204, a second tapered portion disposed adjacent to the first portion wherein the second tapered portion having a second diameter D2 that increases along the y-axis in a direction from the open bottom 216 toward a top wall 212 of the cavity 230, and a third portion having a straight cylindrical sidewall having a plurality of ribs 235 protruding toward the central axis of the cavity, the third portion of the inner surface of the cavity disposed adjacent to the second portion and having diameter D3 that is equal to or greater than the diameter of the ball.