I started out a few years ago with a vacuum of 3-4. I have gradually increased the pressure and duration.
I now pump every morning for 2 weeks (then a week off) using a pressure of 19-20 , holding the pressure for over a half hour
My cock was 7.5 inches long when I started , and only filled a 1 3/4 tube
Now my cock is 9 inches long and fills a 2 1/4 tube ,no puffing or doughnut, my cock head is 2.1/4 wide and 2 inches long.
As far a performance is concerned, I can perform as long as I like (or she likes) ,my erections are full and harder than ever
My ejaculations are very forceful, with 8-10 strong shots,
I am 55 years old
I cannot recommend this but it works for me.