The former uses the peripheral nerves and the lower parts of the spinal cord, whereas the latter uses the limbic system of the brain. These pumps should be distinguished from other penis pumps (supplied without compression rings) which, rather than being used for temporary treatment of impotence, are claimed to increase penis length if used frequently, or vibrate as an aid to masturbation. The man's comfort level is also frequently a factor, especially in maintaining an erection.
More than nine clinical studies performed by six universities and academic hospitals on this purified extract have confirmed the herb's beneficial effect. The vacuum forces blood into the penis, which in turn causes an erection. Men with primary impotence have never had sufficient erections for satisfactory intercourse.