CUSTOMIZE: Choose to receive change air filter reminders, change out the decorative accent color with interchangeable white and gray accent pieces, and select display settings to optimize this thermostat for home. The RTH21B is a directly replacement the RTH2510, and replacement for the RTH2410 offering personalized programming of 7-day, 5-1-1 day, 5-2 day or 1 week schedule options SCHEDULE: Personalize programming in 7 day, 5-1-1 day, 5-2 day or 1 week options - there's even a non-programmable option EXPERIENCE: A large screen and clear font enhance daily use INSTALLATION: The UWP wall plate provides an easy install process and simplifies future device upgrades FEATURES: Flexible scheduling, backlit display, custom display settings, change filter reminder, extended 32°F low-heat setpoint, 1-year warranty COMPABILITY: 1 Heat/1 Cool, 750 mV, hot water heat, forced air (gas, oil, or electric) [does not work with electric baseboard heat (120-240V)] POWER: 2 AA batteries (not included)