This is the amplifier that boosts a cell phone's reception 20X while driving. Unlike other models that that only boost 2G or 3G signals, this one is optimized to amplify 4G LTE signals for Verizon or AT&T cell phones (also boosts 3G and 2G signals for nearly all U.S. carriers). It improves bi-directional signal strength in weak-signal areas, minimizing dropped calls and maximizing data speeds. The amplifier plugs into a car's DC power source and connects to an external antenna that magnetically attaches to your car's exterior. Placing a cell phone in the booster's cradle increases the gain up to 26 dB, but requires no physical connection because it relays calls wirelessly, allowing use of a Bluetooth headset, wired headset, or speakerphone. Specify Verizon or AT&T service. Amplifier: 4 1/4" H x 2 1/2" W x 2 1/4" D. (2 1/2 oz.)