Nokia Lumia 900 AT&T GSM Unlocked 4G LTE RM-808 Windows 7.5 Smartphone - Cyan Blue 3G - HSDPA 850 / 900 / 1900 / 2100 Display - 480 x 800 pixels, 4.3 inches (~217 ppi pixel density) Display Type - AMOLED capacitive touchscreen, 16M colors Internal Memory - 16GB storage, 512 MB RAM CPU - 1.4 GHz Scorpion Unlocked cell phones are compatible with GSM carriers like AT&T and T-Mobile as well as with GSM SIM cards (e.g. H20, Straight Talk, and select prepaid carriers). Unlocked cell phones will not work with CDMA Carriers like Sprint, Verizon, Boost or Virgin.