Penis pumps are bought by men wanting help to achieve better erections for sex (or masturbation).  Many have found these devices to be helpful for curing erectile dysfunction, impotency, and even premature ejaculation problems.  A good penis pump should not only be able to get your cock erect and ready for action, but actually add some length to it as well.  

Penis Pumps come in a variety of forms and prices but generally work by forcing blood into the penis via vacuum sucking.  Many believe that the pumping action will also strenghten the muscle tissue of the penis, even long after use.  You can take a look at over 20 different penis pumps here.