Apple iPhone 4S 8 GB Unlocked, Black GSM/GPRS/EDGE (850, 900, 1,800 1,900 MHz) Quad-band 3G UMTS/HSDPA/HSUPA (850, 900, 1,900, 2,100 MHz) Retina display 3.5-inch (diagonal) widescreen Multi-Touch display 960-by-640-pixel resolution at 326 ppi 8-megapixel rear camera; 0.3-megapizel VGA front camera Apple A5 chip 800 MHz dual-core, 512MB DDR2 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.