Huawei Duplex U8520 was officially announced in October 2011, Device released in October 2011Mobile Network Support and BandHuawei Duplex U8520 have Dual, (Mini-SIM) Card Slots,Huawei Duplex U8520 support all GSM Based network providers. Huawei Duplex U8520 mobile device support 2G Band Frequency at GSM 850,GSM 900,GSM 1800,GSM 1900 and Hight Speed 3G Network Band at HSDPA 850,HSDPA 900,HSDPA 1900,HSDPA 2100, SIM1-900/2100 only,comes with network handling support