I tried this with my partner, and he loved it. I made sure to use lots of water-based lube, which made it work so well. I slowly moved the cup up and down his shaft, and he loved it. He said the nubs feel amazing. The sleeve moves around smoothly, and the silicone is soft. He came 4 times in 30 mins with a few breaks in between. It is easy to remove the sleeve and clean it, too. Using this, in combination with eating his ass, really got him going. He absolutely loved when I stroked his cock with this robó stroke with ramming my tongue in.
That’s the quickest way for a man to cum, in my experience.