Never again Becherklau: This cup can be used only with the direct plug.
You nervous your colleagues to death because they cup your fellow users constantly in the office? Then this cup may be helpful:
The stoppered Beecher has a strategically placed hole in the bottom half, which can only be closed by the appropriate plugs. These plugs but you can easily carry on your key ring, so that no one except you can use the cup, since any content boils down simply. So you'll never have trouble finding a mug in the office kitchen.
The cup is completely made of ceramic and the plug made of soft plastic with a key ring.