This is the Thermometer half of the FE390. One side has a 3/8" Barb and the other has a 1/2" fnpt. Add a H616 barb or use alone or thread on to a 1/2" npt fitting. It is used to measure the temperature on the outflow side of your counterflow wort chiller.Howlong should I apply oxygen while transferring to the fermenter?We recommend youtransfer half of your wort to your fermenter before applying inlineoxygen (O2) to your wort transfer. If you apply O2 the wholetime while transferring you are wasting O2.