A connector includes a cage that has two side walls, a top cover and a rear wall that are combined to form a hollow enclosure. The enclosure is separated into two module-receiving bays by at least one spacer with a top and bottom wall that extends between the sidewalls to form a central portion between a top and bottom bay, the central portion acting as an air passage between a front face and the sides of the connectors. Air openings are formed in the sidewalls of the cage assembly and they communicate with the central portion. The bottom wall of the spacer is provided with a large opening that extends a substantial distance of module-receiving bay and provides an air flow path from the air openings to the bottom module-receiving bay. An insert with apertures in communication with the central portion can be positioned.