The PEX4S553B 4-Port PCI Express Serial Card (with breakout cable) lets you add 4 RS232 serial ports using a single PCIe expansion slot. The PCIe Serial Card includes a 1-to-4 break out cable, which enables you to add 4 serial ports to a single low profile slot. The serial adapter card features a native single-chip design that provides optimum reliability and speed, reducing the CPU load by up to 48% over conventional bridge-chip serial cards - a cost-effective solution for connecting legacy serial devices to PCIe-enabled computers. The multi-port serial adapter includes both full profile/height and low profile/half-height brackets for compatibility with standard and small form factor computers, and is compatible with a broad range of operating systems, including Windows 7/Server 2008 R2, 2003/Vista/XP (32 and 64 bit), Linux Kernel 2.6.11 and up, as well as MAC OS 10.5 and above. This product is a replacement for the PEX4S552B card.