Vacuum pumps are a separate category of intimate devices. Unlike penis extenders, they have an absolutely different working principle and mechanism of influence. Usually, the penis pumps have the form of a transparent cylinder in which the organ is placed and air is pumped out with a rubber pump ball or mini-hand pump and thereby creates a vacuum that causes a strong flow of blood to the tissues of the penis, resulting in an erection immediately. Thanks to this property, classic vacuum pumps were originally developed as a sex toy for stimulating an erection before sexual intercourse. But over time, men have noted a gradual increase of penis and vacuum pumps were started to be used as a device for a real increase the penis. There are 2 main types of pumps - classic air and water pumps (hydro pumps). The latter use warm water as working medium, rather than air, which has a number of significant advantages, read more on the page of the description of the Bathmate Hercules water pump.