COML 106U-D25 is a one-channel 5V/3.3V PCI bus serial communications card. It comes with a 16850 UART, which provides deep 128-byte FIFO buffers and makes programming easy because it emulates the more common 16550 UART.
COML 106U-X-D25 is similar, but it comes with a 16C950 UART, which adds isochronous communication, 9-bit protocols, and programmable choice of transmission speed. We recommend it for savvy programmers.
The cards ship have standard-height backplates, but for smaller chassis they also ship with low-profile backplates (only 8cm high).