A method of assembling a reconstitution device (10) comprising: providing a receptacle (12) having a lip (15) surrounding an opening inserting a stopper (18) into the opening of the receptacle providing a cap (24) having a first end and including flexible legs (30), and a second end opposite the first end inserting a C-clip (34) into an indentation (25) at the first end of the cap (24) sliding the first end of the cap (24) over the stopper (18) and the lip (15) of the receptacle (12), wherein the C-clip (34) allows the flexible legs (30) to expand as the flexible legs (30) pass over the lip (15), and allows the flexible legs (30) to contract after passing over the lip (15) to secure the cap (24) to the receptacle (12).
