Samsung Galaxy S II i777 16GB GSM Android Smartphone Unlocked GSM 850 / 900 / 1800 / 1900, 3G Network: HSDPA 850 / 1900 / 2100 4.3" Super AMOLED Plus Multi-Touchscreen w/ TouchWiz UI v4.0 and Corning Gorilla Glass Android v2.3.4 (Gingerbread) OS, Dual-core 1.2 GHz Cortex-A9 Processor 8 Megapixel Camera (3264 x 2448 pixels) + Front-Facing 2 Megaixel Camera and Video 16GB storage, 1GB RAM + microSD slot expandable up to 32GB 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.