Ulefone Unlocked Smart Phone 5.5 Inch Quad Core MTK6582, 1GB, 8GB, White Unlocked world GSM phone. 3G - 850/2100, 2G -850/900/1800/1900. Compatible with at&t, T-Mobile, Straight Talk, Simple Mobile and other GSM networks. Please make sure your SIM card is not locked with PUK code 3G - 850/2100 bands. Fully compatible with at&t at 3.75G, compatilble with T-Mobile at 2G. For other network such as Straight Talk, Trac fone, Simple Mobile or Net 10 will require a manual APN setup Free Tether - Use your 3G data service as a WiFi hot spot and connect your notebook, ipad or other device for free. No need to pay monthly tether fee Dual SIM Card Dual Standby(one Micro SIM card and one standard SIM card) Operation System Android 4.3 CPU MTK6582 Cortex-A7 Quad Core 1.3GHz GPU: Mali-400MP 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.