A penis pump is a device that creates a negative pressure inside a cylinder to promote blood flow and temporary enlargement of the erectile tissue. A penis pump is often used to support and strengthen an erection, as well as as part of the treatment of erectile dysfunction. The size of the penis may temporarily feel larger. There are many different types of penis pumps. When choosing a pump, note that the larger the tank is compared to the size of the penis, the greater the negative pressure created at once and thus the stronger the effect . Pump seals are available as spare parts.