The stoppers arrived so quickly! I used this to run a water pump in a stone fountain. I sliced through the stopper so that I could thread a sealed waterproof low-voltage power connector into the hole, then inserted the stopper into the bored hole with the wire threaded into the bottom of the fountain. I added a bit of silicone to the wire in the hole as a precaution for watertight fit. Now I have a nice water feature with a pump and low voltage light in the fountain, and the electric power threaded down through the bottom of the fountain. Two weeks later all is watertight. Beautiful!