Trump wants a new FBI director. What to know about their 10-year terms.

President-elect Donald Trump’s announcement that he plans to nominate a fervent ally to lead the FBI was unusual for many reasons. Chief among them: The position wasn’t actually slated to be open for another three years . The job of FBI director comes with a decade-long tenure that is an outlier among presidential appointees.

Here is a brief primer on why that cap exists and how it has worked over the years..