The vacuum pumps work, that is, they create a vacuum and draw blood up into the penis. A kind of wide rubber band is used to hold an erection for those with ED and must be removed once the sexual relations are over. I cannot recommend brands, and I would see no special need for electric, but it might be your personal preference after studying the pros and cons. Those without ED often use the pumps for the fun of it, to gain an erection anytime.
Vacuum pumps work by decreasing the outside pressure surrounding your penis. Decreasing the opposing pressure causes the internal pressure (caused by blood) to increase. This enables your erection to be slightly larger than normal. (You may notice when on an airplane that your flacid penis is larger, which is caused by the same decrease in air oressure). So any device, mechanical or electric, that creates a vacuum will work. The choice is more a matter of convenience.
I should mention, since the question is often asked, that penis pumps will not permanently increase your size, it only works while attached.
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