If lung cancer doesn’t scare a man out of smoking, then maybe his penis shrinking will do the trick.

According to BuzzFeed’s YouTube video, “Everything You Know About Penises Is Wrong,” smoking can decrease penis length by up to 1 centimeter. That’s just one of several facts the video runs through. In case you’re wondering just how smoking causes a man’s member to shrink slightly, though, it’s actually the erect penis that becomes shorter.

Smoking constricts the arteries, which limits blood flow to the penis. In a 2010 study, researchers at the Boston University School of Medicine studied 200 erect men and found that smokers had shorter erect penises. One centimeter might not seem like much, but every bit of length might mean more to the less-endowed.

On the other side of the spectrum are those over-endowed. Diphallia, or two fully functional penises, affects one in every 5.5 million boys in the United States. Johannes Jacob Wecker, a Swiss physician, discovered the condition in 1609. Men with diphallia can achieve erections in both penises and ejaculate as well.

In fact, as one Reddit user with diphallia wrote on the site’s “Ask Me Anything” page, he actually suffers an inflamed prostate if he doesn’t ejaculate every one or two days. That’s double the semen, so he’s forced to “get all the excess out,” otherwise he feels painful bloating.

Watch the video below to learn other facts about penises you probably never imagined (or didn’t want to) — like the fact dead people can both achieve an erection and ejaculate.