Danfoss RAS-D Sensors thermostatic radiator sensor, OEM order code 013G5128 — a self-acting thermostatic operator (sensor head): the liquid-charged sensing element expands and contracts with room temperature and drives the valve cone, throttling flow to hold the set room temperature with no external power. It fits Danfoss RA radiator valves via the RA connection (ra-click fixing) and needs no wiring or batteries. Temperature setting range 8 °C to 28 °C; sensing charge liquid; housing colour Chrome. The head provides built-in frost protection (holds a minimum setting at the snowflake position), maximum/minimum temperature limiting and set-point locking with concealed pins under the dial, a positive shut-off (0) position that fully closes the valve. Genuine Danfoss part; technical data quoted verbatim from store.danfoss.com (code 013G5128). OEM P/N 013G5128, EAN 5702420049984. HS 9032.10 (thermostats). Modulates refrigerant flow to the evaporator in response to superheat at the evaporator outlet.