Pcie X16 -

PCIe boards can fit into slots designed for their lane configuration or higher Plugging a x4 PCIe into a x16 slot is acceptable

PCIe compatibility and performance generates a LOT of confusion In Explaining PCIe Slots

slot doyanbola Buy PCI Express X1 to X16 Low Profile Slot Extension Adapter

slot jago89 The Riser from Dell™ fits into the PCI-E slot of your Dell System Riser cards are used to extend a slot for a chip or card in a fully loaded computer