Honeywell #T87N1000, Round Non-Programmable, 1H/1C, Mechanical ThermostatHoneywell #T87N1000, Round Non Programmable, 1H 1C, Mechanical Thermostat The Round T87N thermostats provide electronic control of 24Vac heating and cooling systems with the classic twist to set dial. Features Mercury Free Classic Styling Premier White Separate temperature setting and thermometer The T87K heat only works with 2 or 3 wire heat only systems The Easy To See has enlarged scale and raised numbers plus it clicks at every 2 F change