A Vacuum Erection Device (VED) or, "cock pump," consists basically of a cylinder (usually acrylic and preferably clear acrylic rather than opaque) which is attached by a small hose to a pump which can be either hand-operated or electric. Having a vacuum gauge on your pump is a good idea, especially for newbies to pumping. Pumps range in price from cheap and not-at-all durable units sold in adult stores for as little as US $20 (not recommended) to electric models complete with pulsators for which you can spend US $ 600 or more. A very durable and well-built hand pump can be purchased for about US $ 140, including pressure gauge, hose, and a cylinder sized to your own erect penis's specifications.
The process is simple. When you insert your penis into the cylinder and create a seal at the base opening (the cylinder resting on your pubic area) air is then gradually removed by pumping and a vacuum is created inside. The penis then expands both in length and in girth attempting to fill the vacuum space within the cylinder. And, because of the vacuum and over time, your penis becomes larger than it would normally with a sexual erection. Blood supply is increased and varying amounts of lymphatic fluid also expand the organ.
There are men whose PE routine consists of vacuum pumping only. Many of these men claim permanent penis size gains over time, but whether these gains are indeed permanent is debatable. Most admit that some modified maintenance program of pumping is necessary to keep whatever gains are created. The timing of pumping sessions varies with each user. Some men pump for short durations, others for many hours at a time, taking only short breaks.