An electrical connector system with a receptacle and plug. The receptacle has a metal housing encircling an insulative housing. A side wall of the metal housing is separated from a corresponding side wall of the insulative housing, leaving a groove. The plug has a wall, extending from an insulative housing of the plug, parallel to a paddle card. The metal housing may be shaped to engage with the wall during mating of the plug and receptacle, facilitating alignment of the paddle card and plug interface of the receptacle. The wall may also carry latching components, which may latch to corresponding features of the metal housing, reducing the height of the mated connectors in comparison to configurations in which the latching components are mounted to the insulative housing of the plug. The receptacle housing may have asymmetric support parts, providing support in a compact space.