... 'S YOUR CHANCE TO have YOUR OWN PERSONAL portable GPS FOR ANY SURVEILLANCE OF YOUR WORK OR PERSONAL VEHICLE! ... just switch on will immediately start to blocking any GPS tracking device signal in a 1 to 20 meters ... coverage area, You can now be invisible to all GPS devices watching you. So, you can go anywhere,do ... want with freedom. ( This device only block GPS Signal , can not block mobile phone signal)