All you need is one place in your home or office that gets at least one bar of 3G coverage. No extra service fees, no internet connection required; Just a little bit of 3G signal strength and our revolutionary new Cel-Fi system will bring you blazing fast downloads, smooth video and surfing, and improved voice coverage throughout your home or office.High end signal booster, specifically optimized for a Large Office or Multi Level Home - this unit has been designed specifically for a Large Office: High Capacity, up to 60 simultaneous users and 42Mbps data speed. This product has the strongest coverage of any in our product line, for a building up to 13,000 Sq Ft.T-Mobile 4G HSPA+ and 3G dual band (AWS, 1.9GHz: 3gpp band 2 and band 4) - compatible with any T-Mobile 3G or 4G mobile phones - Work also on the iPhone 5 / 4 / 4S - For T-Mobile only. Due to local regulatory restrictions, Cel-Fi is available for delivery within the USA only.Only Smart Signal Booster Authorized by T-Mobile for Use on Its Network. With its full digital solution, it is the most powerful and simplest to install mobile phone signal booster in the market. Simple and easy. Plug & Play, you can install Cel-Fi in 5 minutes. No need of cables, antennas.Obsessively smart: Cel-Fi is obsessed with finding the largest coverage. It surveys and adapts to its environment to get the best coverage. All the time.Our most high tech and most powerful product to date, designed for Office needs. Cel-Fi for Large Office is a full digital advanced technology solution, powered by two custom-made massive parallel system-on-a-chip processors with specialized digital signal processors. Smart Antenna technology that automatically adjusts in real-time to provide the best coverage.