A port assembly for a container storing a sterile fluid to be mixed with a medicament in a vial, said port assembly comprising: a port housing defining a first opening at a first end thereof, said first opening providing access to a cavity defined within said port housing, said port housing defining, at second end, a second opening spaced from said first opening, said second opening providing access to said cavity defined within said port housing, a plug movable from a first closed position at which the plug seals the second opening to a second activated position at which the plug is forced partially into the cavity of the container thereby opening the fluid flow path to the container, an actuator positioned within said cavity of said port housing, said actuator having a proximal end portion and a plurality of sidewall members extending axially from said proximal end portion toward said second end of the port housing, one or more openings being defined between said sidewall members, said sidewall members have a terminal end spaced from said proximal end portion of said actuator, and a central cavity defined by said sidewall members, said actuator adapted to force a stopper associated with a vial into a vial during an activation step; and a retainer positioned in the cavity defined by said port housing, said retainer having a plurality of retaining tabs (520, 522), at least one of said plurality of retaining tabs (520, 522) having a first length adapted to retain a vial in a first, docked position, and at least one of said plurality of retaining tabs (520, 522) having a second length adapted to retain a vial in a second, activated position. a port housing defining a first opening at a first end thereof, said first opening providing access to a cavity defined within said port housing, said port housing defining, at second end, a second opening spaced from said first opening, said second opening providing access to said cavity defined within said port housing, a plug movable from a first closed position at which the plug seals the second opening to a second activated position at which the plug is forced partially into the cavity of the container thereby opening the fluid flow path to the container, an actuator positioned within said cavity of said port housing, said actuator having a proximal end portion and a plurality of sidewall members extending axially from said proximal end portion toward said second end of the port housing, one or more openings being defined between said sidewall members, said sidewall members have a terminal end spaced from said proximal end portion of said actuator, and a central cavity defined by said sidewall members, said actuator adapted to force a stopper associated with a vial into a vial during an activation step; and a retainer positioned in the cavity defined by said port housing, said retainer having a plurality of retaining tabs (520, 522), at least one of said plurality of retaining tabs (520, 522) having a first length adapted to retain a vial in a first, docked position, and at least one of said plurality of retaining tabs (520, 522) having a second length adapted to retain a vial in a second, activated position.