Double the volume of your tunes without any batteries! The iPhone Horn Amplifier requires no batteries, instead it acoustically amplifies your iPhone's output with its unique design. Perfect for a bedroom or bathroom, the iPhone Horn Amplifier also acts as a dock and can hold your iPhone horizontally or vertically. This great iPhone accessory comes in purple, green, pink, or white, all great colours to spice up and turn up the volume! Compatibile with iPhone 3G, 3Gs, 4, 4s