Easy to install white mechanical heating thermostat that is mercury free and works with most single stage heating systems. Works with most 24 volt and millivolt systems. Features a decorative wallplate, mounting hardware and installation guide. The unit is also compatible with gas or oil heat, Millivolt heat only systems with floor or wall furnaces, standard heat only systems and hydronic (hot water) zone heat with 2 wire design. Terminal designations listed as: R and W.