Danfoss RA2920 Fixed Sensor Thermostatic Radiator Valve Head Only 013G2920 Danfoss RA2920 Fixed Thermostat Sensor incorporating Frost protection, limiting and locking of temperature set-point, connection with clamping ring and Allen screw. RA2920 temperature range 5-26°C. Tamperproof Sensor. Use with RA-N, RA-FN or RA-G valves.