Grado GW100x Wireless Series Open HeadphonesThe GW100x Bluetooth open back headphone is Grados 3rd edition of this award winning headphone. The GW100 series was the first and is the only open back Bluetooth headphone on the market, offering superior sound than its closed back contemporaries. No compromises with sound it's a Grado. This GW100x uses Grados 4th generation driver which features a more powerful magnetic circuit, a voice coil with decreased effective mass, and a reconfigured