While Justin Bieber isn't the tallest celeb in Tinseltown, keep in mind that he's rolling with a pair of 6'9" dudes in the pic above!

On Sunday Biebs and close pal Kevin Durant went shopping at Barneys New York, and we imagine it was quite comical to watch the pop singer and the NBA superstar picking out clothes together. I mean, Kevin wears a size 17 shoe and last we checked Biebs, who is somewhere around 5'9", is just a 7.5!

Over the weekend the boys posted a video of Biebs shooting Durant with a nerf gun (the post has since gone missing from social media), but apparently Bieber reveals why Durant is his fav target. "Cuz he's giant," the pop star says. Boys will be boys, even if they're famous millionaires...

We snagged the video that Bieber removed from Instagram -- check it out ...