Applicable for all the GSM (900-1800HZ) mobile phones with inner antenna such as Nokia 8250 and 7210, no battery needed. When the mobile phone is receiving or sending signals the LEDs inside the product sticked on the back of the mobile phone will flash continuously. The product can give you a reminder even if the alarm of the mobile phone is shut down. What’s more this product can reduce the radiation of the mobile phone to human’s brain. Customer required Logo can be imprinted on the product or its packing card. What a wonderful design! And what a wonderful gift to your friends! Many LED colors for you to choose: red, yellow, green, blue and white.