By using a Aspirator or Venting Peg to vent your cask when it is first pierced you stop any wasted beer from the initial surge caused by excess CO2. Simply knock into the cask with the valve in the closed position and slowly throttle the opening of the valve to allow the excess gas to escape in a controlled way. In addition there will now be no mess as any froth is vented down the tube where it can be collected and disposed of.
DIMENSIONS:
Height 100mm.
Width 80mm
