HTC 8S Factory Unlocked A620 Black/White Windows Mobile 8 2G Network GSM 850 / 900 / 1800 / 1900 3G Network HSDPA 900 / 2100 OS Microsoft Windows Phone 8 Primary 5 MP, 2592...1944 pixels, autofocus, LED flash, check quality Card slot microSD, up to 32 GB Internal 4 GB, 512 MB RAM 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.