Internal Host interface: PCIe Output interface: Serial Add 4 RS-232 serial ports to your standard or small form factor computer through a PCI Express expansion slotThe PEX4S553 4-Port Native PCI Express RS232 Serial Adapter Card with 16550 UART lets you add 4 RS232 (DB9) serial ports, using a single PCI Express expansion slot.Based on a native single-chip design, this 4-port serial adapter card allows you to harness the full capability offered by PCI Express (PCIe), while reducing the load applied to the CPU by as much as 48% over conventional bridge-chip serial cards.The RS232 Serial Adapter Card includes 4 half-height/low-profile brackets, allowing the card to be installed into almost any PC case, regardless of form factor.Backed by a StarTech.com Lifetime warranty and free lifetime technical support.The StarTech.com Advantage- Native single-chip, single lane PCI Express chipset delivers true PCIe performance, up to 48% more efficient than bridge chip designs- Standard and low profil