Plastic Pressure Reducing Valve - 5 bar

Plastic Pressure reducing valve (or Pressure-limiting valve) is typically installed inline before water components (such as filter systems, filter housings, plumbed-in water dispensers, etc)  using 1/4" piping, to protect the components from damage due to high-pressure or water "hammering". 

The plastic pressure reducing valves are all set to a specific pressure rating, which the valve will not allow the water pressure to exceed. In this case, the maximum pressure setting is 5 bar (70psi), so the valve will not allow the water that will feed to the components after the pressure valve to go above 5 bar.