The silver colored version of the Fiio A3 - Portable Headphone Amplifier is designed for mobile Hi-Fi listening applications and is compatible with a wide range of headphones, earphones, and other in-ear monitoring systems. The all-aluminum alloy body and chassis of the amplifier shields against electromagnetic interference and the built-in rechargeable 1400 mAh battery provides approximately 16 hours of operation on a four-hour charge via mini USB port. For I/O, it features an 1/8" stereo auxiliary input and an 1/8" stereo headphone output.