The StarTech PEX4S553B PCI Express x1 Low Profile RS-232 Serial Adapter Card is a high-quality serial card designed for easy port expansion in computers. With its compact and low profile design, it is perfect for adding a single serial port to your system. The card is compatible with StarTech products and is ideal for connecting peripheral devices that require an RS-232 interface. The product is a unit by itself and comes with a PCI Express x1 compatibility, making it a versatile addition to any computer setup.