The 12x Series of temperature sensors come in a wide variety of ranges, connections, materials, and sensor types. The B12x models come with single or dual switches with an adjustable external dial to set the range. These are immersion type sensors. The C12x models are single switch immersion sensors with internal range adjustments. The E12x series are the same as the B12x series except that they have a bulb and capillary sensing option. The F12x also comes with a bulb and capillary sensing option, but it has internal setpoint ranges.