The HP BladeSystem PCI Expansion Blade provides PCI card expansion slots to an adjacent c-Class server blade. This blade expansion unit uses the c-Class mid-plane to pass standard PCI signals between adjacent enclosure bays, to allow a c-Class blade server to add off-the-shelf PCI-X or PCIe cards. Customers would need one PCI Expansion Blade for each c-Class server blade needing PCI card expansion. Any PCI card from third-party manufacturers that works in HP ProLiant ML and HP ProLiant DL servers should work in this PCI Expansion Blade.