A closed loop dispensing system comprises a connector connectable to a container for selectively dispensing the fluids from the container. The connector includes an outer cap having a first passage with an interior surface. The first passage can have variable cross-sectional areas over different regions of the first passage. The connector comprises a plug slidingly movable between an open position and a closed position, wherein, the plug allows passage of fluids present in the container in the open position, and the plug prevents passage of fluids out of the container in the closed position. The plug can have a variable cross-sectional area thereby preventing the plug from being disengaged with the outer cap or sliding out of the connector and into the container.