Disclosure: I received this product as part of an advertorial.
I decided to use these cups to swish the water around in my mouth after I brushed my teeth; they worked well for me for that purpose.
I decided not to stack them because when I received them they were hard to get apart; that could of been because of the plastic between the cups for shipping purposes though and they might have been easy to get apart without the plastic in between them if I had decided to stack them.
They also matched well on the sink I used them on. I rotated them out when the cup I was using looked too dirty and switched it with the clean cup. I think I have washed both of them at least twice and they have stayed rust-free.
My review = 4.5 out of 5 stars
I received two of these cups for free using Tomoson.com. Regardless, I only recommend products or services I use personally and believe will be good for my readers.