Noting the success the British Royal Marines had with their "Personal Role Radio'' in Afghanistan, and last year in Iraq, U.S. Marines who recently returned to Iraq have brought the same personal radio system with them. The marines purchased 6,499 of the radios, at a cost of $770 each. The radios have a range of about 500 meters (or three floors inside a building). The earpiece and microphone are built to fit comfortably into the combat helmet. The radio set itself, about the size and weight of an iPod, hangs off the webbing gear on the chest. Two AA batteries power the radio for 24 hours. The users have 16 channels to choose from and a form of frequency hopping is used to make it very difficult to listen in on transmissions. A small, wireless, "talk" button is affixed to the soldiers weapon so that operation of the radio is hands free. This kind of radio is particularly useful in urban warfare, and marines are currently using them in Fallujah and other towns in the Sunni areas west of Baghdad. The radio makes it possible for marines to more quietly go after enemy troops. Without the radio, you are constantly shouting to let people know where you are and what you are doing. But all this noise alerts the enemy as well. With the personal role radio, you have the advantage of silence.