The headphone amp is compact and light-weight design, not bigger than a hand of the adults, easy to use and carry. Features: Helps to deliver high-quality guitar sounds, retaining the sound output of the guitar. Designed with 3 knobs: blend / tone / volume knob. AUX jack lets you connect an external audio device to this jack. Uses the headphone jack to connect headphone, portable speaker or mixer. Powered by the built-in battery. Comes with a USB cable for charging the item. Compact and light-weight design, not bigger than a hand of the adults. Specifications: Power Supply: Built-in 180mAh 3.7V rechargeable battery Working Current: 37mA Item Size: Approx.8 * 8 * 1.2cm / 3.1 * 3.1 * 0.5in Item Weight: Approx.33g / 1.2oz Package Size: Approx.14 * 11 * 2cm / 5.5 * 4.3 * 0.8in Package Weight Approx.70g / 2.5oz Note: The headphone is not included. Package List: 1 * Headphone Amp 1 * USB Cable