Amazon.com: TP-Link AC750 WiFi Extender (RE220), Covers Up to 1200 Sq.ft and 20 Devices, Up to 750Mbps Dual Band WiFi Range Extender, WiFi Booster to Extend Range of WiFi Internet Connection :
How to check your Unifi Wifi network for unwelcomed device and block them on TP-Link router - Barzrul Tech