The basic mechanism of vacuum devices consists in creating a partial vacuum so that the blood penetrates the penis, producing an erection. The device consists of a plastic cylinder into which the penis is inserted, a vacuum pump and an elastic band placed at the base of the penis in order to prevent the blood from receding (fig. F). The erection that is produced is effective in 67-90% of the cases, but only 34-68% of the patients are satisfied with its use. The principal problem is blockage of the ejaculation due to the constrictive action of the elastic band on the urethra.