Is the O shaped Uvtuvo Washing Cup kosher for Netilat Yadayim according to all opinions? If not, what are the sources and issues so one can make an informed decision? Thanks!
If you have a "cup" that has a hole in it that leaks water, you may only pour out water to wash your hands from that hole [if its possible to pour from there]. Any part of the cup above the hole, is not considered a kosher utensil for washing. [See Shulchan Aruch A"H 159/2]
In your case, when the cup is standing on it's base, the water will only go up to a certain point. Anything above that point would not be considered a kli - utensil. Therefore, if the water you are washing your hands with, is coming above the top, it would not be an acceptable washing. I would think it is difficult to be careful about this, and not advisable to use for washing on a regular basis.