Boss Audio Systems MCBK470B Motorcycle Bluetooth Speaker System - Class D Compact Amplifier, 3 Inch Weatherproof Speakers, Volume Control, Great for Use With ATVs and 12 Volt Vehicles BLUETOOTH: Play and control a vast library of your favorite music using your smartphone or MP3 device, plus plug into apps like Spotify and Pandora wirelessly AMPLIFIER: A Bluetooth, compact, weatherproof, class D amplifier is included. WEATHERPROOF: The MCBK470B has been outfitted with the latest weatherproofing techniques for protection against the elements SPEAKERS: Also included are four 3-inch, black, full range speakers. The adjustable brackets will fit handlebars from ranging from .75” to 1.25” PLAYBACK: A 3.5 mm auxiliary input is compatible with audio outputs of smartphones and MP3 players