Add 4 rs 232 serial ports to your standard or small form factor computer through a pci express expansion slotr r native single chip single lane pci express chipset delivers true pcie performance up to 48 more efficient than bridge chip designsr standard and low profilehalf height brackets included to ensure fitment in any systemr r the 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 slo