【SPECIALLY CUSTOMIZED FOR CAR KEYS】No fancy functions. Todoxi faraday box effectively shielding all signal in the box which prevent criminals from using key fob skimming tools to access your vehicle. 【BEST SIZE 】The signal blocking key box can hold 5-7 car keys including key rings and house keys. A bit smaller, and higher cost performance. 【HOW DO I KNOW IT WORKS?】You can test it by yourself! Simple place the car key into the box, and you will find no reponse from your cars.