these infrared heaters are made out of ceramics. these emitters have a Nichrome (NiCr) wire directly casted into ceramic and they produce temperatures from 300 deg F to 750 deg F. The wavelength produced with at these temperatures is between 3 6 microns. They feature a glazed surfaced to avoid for protection from oxidation and corrosion. Typically they need 10 15 minutes to reach full operating temperature.