The Aqua Medic Regulation Valve is 6mm (1/4") in-line control valve for finely tuning flow rates into low-flow bypass filters like our Calciumreactors and Nitrate Reductors. The Aqua Medic Regulation Valve also works for the adjustment of gas flows as well, as into Aqua Breed hatching systems, Plankton Reactors, Turboflotor Protein Skimmer venturi or Ozone Generators.