Nice product! Very fast delivery and amazing customer support. The seal could be better but then it would not be a one use item. I`m satisfied.
I tried it as it comes, and then i tried the silicone directly (outside the structure), and i prefer the last one. The sensation is very good; not the best i've tried, but definitely the best cost/benefit ratio. For those who don't have a big budget for these things i'll say go for the vacuum cup, you won't be disappointed.
I have been using it for years there is nothing better out there