The ear monitors can amplify sound and have a top knob to control the volume. It also comes with a 3.5 mm stereo output jack that fits your favorite headphones and earplugs. This is a lightweight and portable headphone amplifier that can be easily clipped to your waist, whether you arefixed in one position or moving around on site. You can adjust the volume andchannel at any time. P2 uses XLR / TRS combo input connectors with locking mechanism to prevent XLR cables from accidentally disconnecting. It also supports stereo / mono switching to meet different monitoring needs. The in ear amplifier has an extremely compact body and is made entirely of metal. Input: XLR - 1/4inch locking combination jack Output: 1/8inch TRS, stereo Impedance: 0.5 Maximum output: 2x100 mW 16 Battery: 3.7v/500mmAh (polymer lithium battery) Charging voltage: 5V Battery life: 6-8 hours Colour:Black Material:Metal Package Contents: 1 x headphone amplifier 1 x USB charging cable 1 x storage bag(Colors and styles are random, no specified colors or styles are accepted) Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.