Horn Stand Speaker Loudspeaker Amplifier Silicone for Apple Iphone 4 4g Blue by N MARKET No external power needed,13 dB of volume amplifer Silicone horn effectively enlarges music from your phone Unique design stand amplifier for Apple Phone Holds iPhone vertically and horizontally, functions well in hand-free mode Compatible with the following:iPhone 4 , iPhone 3G S , iPhone 3G