Our SmartDefender™ units for Cell Towers, SmartMeters, WiFi and Geopathic Zones are designed to help reduce the stress caused by the waves emitted by all devices. The smallest SD 5 unit, just 2" x 0.3" and 0.6 ounces, handles a radius of up to 15 feet from the unit. It's easy to carry in a pocket or a purse. The next size up, the 4" model SD 10 weighs 3 ounces and handles a 30-foot radius. The larger 7.5" model SD 50 is perfect for homes and commercial buildings, handling a 150-foot radius..