A Swedish health clinic is distributing free penis tape measures so young men are properly fitted for condoms.

In an effort to promote better sizing and less slippage to prevent STDs, the tape measures were handed out beginning Tuesday, World AIDS Day, according to AFP.

So what's the secret to measuring your privates? Turns out it's pretty simple, but has a special strategy.

"You have to measure the circumference of the penis when erect, not the length," says clinic nurse Eddie Sandstrom. "On our measuring tape you get the measurement in millimeters and a few recommendations for condom types that are suitable."

According to Sandstrom, previous awareness campaigns were never as successful as this one in persuading Swedes t use condoms, calling this particular campaign "more open and a bit more fun."

Sweden was dubbed "Europe's STI capital" in 2013 by the media after a study on infections revealed the country's unsettlingly high rate in STIs.

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