Nokia Lumia 635 8GB Unlocked GSM 4G LTE Windows 8.1 Quad-Core Phone - Black 2G: GSM 850 / 900 / 1800 / 1900, 3G: HSDPA 850 / 1700 / 1900 / 2100, 4G: LTE 700 / 850 / 1700 / 1900 / 2100 / 2600 (Bands 2, 4, 5, 7, 17) 4.5-inch IPS LCD Multi-Touchscreen w/ ClearBlack display and Protective Corning Gorilla Glass 3 Microsoft Windows Phone 8.1, Quad-Core 1.2 GHz Cortex-A7 Processor, Chipset: Qualcomm Snapdragon 4, Adreno 305 Graphics 5 Megapixel Camera (2592 ? 1944 pixels) w/ Autofocus, 1/4-inch sensor size, Geo-Tagging, Panorama + Video Internal Memory: 8GB, 512 MB RAM + microSD Slot Expandable up to 128GB 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.