Comfortably holds two PCIe devices, or one multi-slot device without tipping over. Both cards fit without bumping into each other, and they can be lined up without hitting the cards in the next or previous gridfinity. Some PCI devices will not line up properly with PCIe devices, since the socket was designed to be in a different alignment with the faceplate, so you may want to store PCI and PCIe devices seperately. Should also support AGP or any other slot-in card of a similar standard and size (1.8mm or less).