Ezra Miller interviews are the best! In all my years of covering superhero movies, I’ve never seen an actor geek out about the superhero he’s playing quite like Miller.

While promoting his new movie Fantastic Beasts and Where to Find Them, Miller was asked about the movie magic that makes the Flash fast in Justice League. According to Miller, there’s a 25 foot treadmill that’s bouncy like a trampoline and goes up to 45 miles per hour. Watch Miller completely geek out about it in the video below around the 5:53 mark.

Justice League hits theaters on November 17, 2017.