This is the original WiFi Router Guard invented and designed by Smart Meter Guard. Be aware of copies. The WiFi Router Guard is a custom built Faraday cage that blocks about 85% or so of the EMF or RF waves WiFi Routers emit. Simple and easy to use. The Router Guard is made for most small WiFi routers that are SMALLER than 12 x 9 x 3 inches in size. Please measure your router and make sure there at least "1 inch" space for the cables to fit. The Router Guard does not fit large routers like the Comcast Xfinity or ATT Uverse routers. If your router is larger than this dimension or you have the Xfiniti or Uverse routers please see our "Large Router Guard" product on our web site. Please view the Router Guard image that shows how your router will fit in the Router Guard and the size and room you need for your router to fit in the Router Guard and the cables. Also, please take into account any base structure that is on your router. WiFi Router Cover Measuring RF is complicated. If you decide measure RF, radio frequency, waves please make sure you are measuring in units of micro watts per meter square, uW/m2. Measuring RF is complicated. If you are measuring in units of Gauss, T or mT then you are using the wrong meter and measuring the wrong field. If you decide to measure please use the Gigahertz Solution HF 35C or the Cornet ED88T Plus RF meters. If you have questions on measuring please contact us and we can help you.