Apparatus and methods for lyophilizing and sealing a medicament within a medical delivery device having an opening. The apparatus may include a stopper for sealing the opening. The stopper may have one or more elongated members extending from a base, in a direction that is parallel to a central axis of the base. One or more of the members may be set radially away from the axis and define a coaxial central well. The member or members may define a void. The elongated member or members may engage a device inner wall and support the base away from the opening. The void may provide gas exchange between a device interior and a device exterior. The gas may be a lyophilization byproduct that escapes from the device interior between the inner wall, the base and the member or members. The stopper may be advanced into the device to seal the opening.
