Built-in distortion effect. Designed with 3 adjuster: Level， tone， gain. 0.25in plug， just plug into guitar jack， no need of installation.. Powered by two AAA 1.5 alkaline batteries (not included).Product size: 9.7 * 8.4 * 2.1cm / 3.8 * 3.3 * 0.8in Product weight: 44g / 1.5oz Package Includes:1 x Guitar Plug Headphone Amp 1 x User Manual (English & Chinese)