Nokia Lumia 530 Dual-SIM Unlocked GSM Windows 8.1 Quad-Core Phone - Grey 480 x 854 pixels, 4.0 inches (~245 ppi pixel density) Internal Memory: 4 GB, 512 MB RAM Camera: 5 MP, 2592 x 1936 pixels OS: Microsoft Windows Phone 8.1 CPU: Quad-core 1.2 GHz 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.