A parallelepiped-shaped plastic cover for a PCI express x16 connector array has a top defining a window. Some but not all of the connector array elements are blocked by the top when the cover is positioned over the connector array, so that in the event that the associated computer is not configured for receiving components requiring connections to all elements of the PCI express x16 connector array, a user cannot unwittingly plug such a component into the PCI express connector array but can only plug in, through the window, components requiring fewer than all connector elements.