Netgear Nighthawk M1 Mobile Router Add-On Battery

"All-day mobile WiFi. The Nighthawk lithium-ion battery (5040mAh) works with the Nighthawk M6 and M5 Mobile Routers. Rechargeable and compact to take on the go, you can use this as a backup battery for sharing your mobile router with up to 32 WiFi devices all day long. Compatible with mobile hotspot models: MR6550, MR6450, MR6150, MR5200, MR5100."