Reference:
875U
Like the Sierra Wireless AirCard 875 LaptopConnect card, the AirCard 875U USB modem offers tri-band UMTS/HSDPA connectivity, making it compatible with mobile broadband networks worldwide, with data speeds up to 3.6 Mbps (megabits per second). The new compact, stylish USB form factor allows AT&T to extend wireless service to computers without PC card slots.