Google Nest T5000SF Temperature Sensor & battery - no box, 2

my own system just removed from service * No box * * Includes battery What's it for? What's it work with? "Works with the * Nest Thermostat E or the *3rd gen Nest Learning Thermostat. Helps make sure a certain room is the exact temperature you want it to be. Put temperature sensors in different rooms. And choose which room to prioritize when. Place it on a wall or shelf. Set it up in the Nest app. Then forget that it’s even there" buy with confidence 25+ years selling online fast, careful shipping smoke free, pet friendly home