Actually, there are a couple of devices that might be referred to as penis pumps. One of these works as part of a prosthetic implant system that consists of thin cylinders surgically implanted in the penis into which a saline solution can be pumped from a reservoir that is implanted under the skin of the lower abdomen. When activated, the cylinders fill with the saline solution that creates an erection suitable for sexual activity.
There’s also an external type of penis pump, technically known as a vacuum constriction device. The device consists of an acrylic cylinder that can be fitted over the flaccid penis. A pump, powered by hand or battery, then removes all of the air in the cylinder creating a vacuum. The vacuum draws blood into the shaft of the penis, causing it to become erect. A constriction band can then be fitted to the base of the penis to keep the blood from flowing out until sexual activity is complete. Using the constriction device for more than 30 minutes is inadvisable, according to WebMD.