018F6968, Hum-free coil for valve range B, with extra low noise level , 20W ac, IP67. Clip-on system for fast, easy fitting and removal. Hum-free for installations sensitive to noise, such as heating systems. Built-in rectifier. Encapsulated coils with long operation life. Ambient temperature: Up to +50°C. IP 67 for moist environments with flying lead.