The Grainfather counterflow chiller is used after boiling the wort to cool it down fermentation temperature. The counterflow does this by acting as a heat exchange between the wort and water from your tap as you transfer the wort from your boil kettle to your fermenter. Because this is a one-step process of transferring and cooling, it is more efficient and more sanitary than immersion chillers, and the curved design allows for similar performance to plate chillers without the crevasses that can make cleaning painful.  

Shop Grainfather G30 V3 With Counterflow Chiller Bundle 
Shop Grainfather G30 V3 Without Counterflow Chiller