The 4-door native 4-door Native Native Native Native Native PCI Express Adapter Card Card with 16550 URT PEX4S553 allows you to add 4 RS-232 serial doors (DB9) using a single PCI Express expansion slot. Basate on a native single chip design, this 4-door serial adapter card allows you to exploit the complete features offered by PCI Express (PCIe) by reducing the load on the load on the load CPU up to 48% compared to the conventional serial cards with bridge chip. The RS-232 serial adapter card also includes 4 optional brackets with half-height/reduced profile, with which you can install the card practically on any computer regardless of the form factor.