I bought a Venus 2000 male masturbation machine and love it. I have had it, or its predecessor model, for 9 years now. It is some of the best money I ever spent.
It consists of an artificial vagina made with a transparent rigid outer shell and a soft rubber inner liner. One end is capped: the other receives your lubed penis. The space between shell and liner is connected by a hose nipple to a cycling air/vacuum pump. This pump gives a puff of air into the outer shell, causing the liner to ssqueeze toward the middle. Then it reverses and pulls a brief vacuum, causing the liner to expand toward the outer walls. This alternating compression and expansion of the liner makes the device glide effortlessly up and down your lubricated penis. The really nice thing about it is that you don't even have to be erect to have an orgasm. Because the device will pull your penis into it, and push your penis outward in cyclic fashion, you don't even have to be hard, so it is perfect for guys with erectile dysfunction.
I have no connection to the seller of this machine. I am just a delighted customer. I think it has extended my sex life beyond what would have been possible without it. If I had had a Venus 2000 when I was a teen, I would have thought I had died and gone to heaven! The sensation it produces is similar to a very delicate and sensual blow job.