Sierra International 18-3670 Thermostat Kit - 160&deg; The Sierra 18-3670 Thermostat Kit is interchangeable with the following: GLM 13440. Contains: (1) 18-0929 Thermostat Gasket, (1) 18-2858 Thermostat Gasket, (1) 18-3558 Thermostat. Sierra Thermostat Kit Contains: (1) 18-0929 Thermostat Gasket, (1) 18-2858 Thermostat Gasket, (1) 18-3558 Thermostat Sierra part number: 18-3670 Interchangeable with the following: GLM 13440