Feature: 1. HIGH SENSITIVITY: Headphone amplifier has high sensitivity, ALC automatic level control, 1000 times amplification, so you can hear the faint sound. 2. CLEAR SOUND: Portable headphone amp amplifies your voice with clear, crisp, noiseless, distortion free sound, stylish and powerful. 3. INTERFACE IS 3.5MM: Stereo headphone amplifier direct drive headphones to listen, can be connected to cell phone recording, the interface is 3.5mm. 4. ALUMINUM ALLOY HOUSING: Microphone amplifier with aluminum housing, compact size, storage and carry are very convenient, beautiful appearance. 5. ANTI INTERFERENCE: Headphone amplifier ensures lossless signal as well as strong anti interference performance, very reliable. 6. APPLICABLE RANGE: Headphone amplifier is suitable for teaching, trainers, singers, coaches, shopping malls, presentations, outdoor speeches, etc. Specification: Item Type: Headphone Amplifier Material: Aluminum Alloy Battery: Lithium Ion Battery 502030 (Built In) Capacity: 250 MA Power Supply: DC 5V Interface: Approx. 3.5mm/0.1in Practical Use: Direct Drive Headphones To Listen, Can Be Connected To Cell Phone Recording Size: Approx. 65x53x25mm / 2.6x2.1x1.0in. Package List: 1 x Microphone Amplifier1 x Power Cord1 x Headphone Cable Note: Please allow some error due to manual measurement