iBasso D-Zero MK2 D0-MKII Dual WM8740 DAC Portable Headphone Amplifier with 3.5mm Stereo to RCA Connection Kit Includes iBasso D-ZeroMK2 Headphone Amp, Carrying Pouch, USB cable, 3.5mm to 3.5mm interconnect, OTG cable, silicone strap, 3.5mm Stereo to RCA connection cable, and USA Warranty Card(One Year USA Warranty from Authorized iBasso Dealer) Recommended Headphone Impedance 8-300Ohms 2 Setting Gain Switch for Impedance Matching Rechargeable Li-polymer battery with integrated charging system. Up to 120 Hours of Playing Time When Works as an AMP and upto 10 hours When used as a DAC. Slim and small, it is ultra portable design.