Skullcandy Crusher Headphones with Built-in Amplifier and Mic, Black Sensation55 Driver - The Sensation55 is Skullcandy's patent-pending bass extension driver. Through this driver, the Crusher delivers a powerful and realistic bass experience that transforms your audio into bass you can feel. Connectivity Technology: Wired REX40 Driver - The REX40 is designed from the ground up by their world-class audio engineering team and delivers an extremely smooth frequency response with minimal distortion - tuned for your playlist. Acoustical Porting - Within the construction of the ear cup, our specially designed acoustical porting allows both drivers to move freely, increasing the bass and reducing distortion. Built-in amplifier - No more bulky in-line amplifier. The new Crusher draws its power from a premium battery (AA) powered amp hidden in the ear cup. Adjustable Bass Control - The bass sensation slider on the left ear cup allows you to adjust the sensation levels to your preference or playlist.