It’s the age-old question: “Does size matter?” In the case of Adrian Grenier, it certainly didn’t hurt!

In her tell-all book, “I Didn’t Come Here To Make Friends: Confessions Of A Reality Show Villain”, “The Bachelor” season-16 winner Courtney Robertson reveals that she’s hooked up with the “Entourage” star — and was very impressed with his manhood.

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Of course, when Grenier appeared on “Watch What Happens Live,” host Andy Cohen couldn’t resist discussing the revelation with the actor!

“She said you had the biggest d*** she’s ever seen,” Cohen noted.

But the 40-year-old didn’t seem to mind the interest in his manhood. “I was just glad she got the size right,” Grenier replied, “And she’s seen a couple of them, huh?”

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He went on to add, “You’re always on the edge of your seat waiting for something bad to be revealed about you, and then every once in a while, it’s not so bad.”

Grenier also opened up about working with Britney Spears way back in 1999, when he starred in the music video for her hit “(You Drive Me) Crazy”. Noting that the pop star was “professional” on set despite having “a lot of handlers,” he tells Cohen that he only agreed to star in the video in order to interview Spears for a documentary.

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“It’s called ‘Shot In The Dark,’ and I went to go find my estranged father,” he said of the project.

As for why he wanted to interview the singer? “She has father issues,” Grenier revealed, with no other details given.

Watch the video below to see him reveal more about his time on set with Spears.