The thermocouple and RTD connection heads listed below meet NEMA 4 requirements for indoor or outdoor non-hazardous use to provide protection against dust, rain, splashing and hose directed water. The cast iron heads are coated with a black paint. The paint provides good corrosion and chemical resistance, however, it does not provide UV protection for outdoor applications. The 316L stainless steel head offers excellent corrosion resistance and chemical resistance and is suitable for outdoor applications and meets NEMA 4X requirements. These heads will accept any of the Pyromation 340 series terminal blocks and series 440 RTD transmitter. These heads will not accept the DIN standard blocks or transmitters.