This product includes 2 router units..Battery Cell Composition: Lithium Ion Nest Wifi is a scalable and flexible Wi-Fi system. These Nest Wifi devices work together to blanket your whole home in fast, reliable Wi-Fi and eliminate buffering in every room – with coverage up to 4400 square feet.[1] 1 Wi-Fi router plugs into your internet provider’s modem to create your Wi-Fi network. The other extends the wireless network and keeps your connection fast to devices in every room. For more coverage, add Nest Wifi routers or points to your system.