Imagine the perfect low-maintenance birth control: You take it once, it prevents pregnancy for years, and it has shockingly few side effects. Yes, it exists, and it’s called an intrauterine device (IUD). But while many female ob-gyns swear by them, only about 5 percent of U.S. women who use contraception choose an IUD. Experts chalk it up to confusion and urban myths. The facts:

How do these things even work?

There are two types of IUDs in the United States: ParaGard, which lasts 10 years and contains copper, creating a toxic environment for sperm; and Mirena, which lasts five years and releases the hormone progestin, making it hard for sperm to reach an egg, says Katharine O’Connell White, M.D., assistant professor of gynecology at Tufts University School of Medicine.

So, Where does it go?

A doctor places an IUD in your uterus (its threadlike removal strings hang down just a tiny bit from the cervix). Don’t worry, it doesn’t bounce around up there: “The uterus is like the vagina—it expands when something is in it, but is collapsed the rest of the time,” says Dr. O’Connell White.

And they’re effective?

Extremely. “IUDs prevent 99 percent of pregnancies, but they’re completely reversible,” says Vanessa Cullins, M.D., the VP of medical affairs for Planned Parenthood. Studies show they also can decrease the rate of uterine cancer and ease painful or heavy periods, says Melissa Gilliam, M.D., professor of obstetrics and gynecology at the University of Chicago.

Are IUDs pricey?

Getting one can cost up to $1,000 without insurance, but it’s covered by many plans, so your out-of-pocket cost could be between $20 and $200. That means if you use it for more than a year, you’ll wind up paying less than you would for any other prescription birth control method.

Will my guy feel it?

Most likely not—an IUD is too far up. In rare cases (and, ahem, endowments), men may feel the strings, but your doctor can trim those more.

I heard it hurts!

What’s typical, say the ob-gyns we spoke to: a few hours of what feels like menstrual cramps following the five-minute in-office procedure. Taking Motrin before going in will help. Some women do have sharper pains, but, says Dr. Gilliam, “it is a quick bit of discomfort in exchange for years of highly effective birth control.”