Gregor Clegane and Conor McGregor

Ever wonder why sports have weight classes? If a guy is tough, they’re tough, right?

Well, look no further than the video above for a brief but undeniable argument in favor of weight classes. Because what you’re watching is the UFC’s number-one featherweight contender, Conor McGregor (5’9″, 145 pounds) doing battle with Hafbor Julius Bjornsson (6’9″, 240 pounds) — the latter of whom is perhaps better known as “The Mountain” from “Game of Thrones.”

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Some say the bigger they are, the harder they fall. But The Mountain isn’t falling anywhere, and if anything he just seems amused when McGregor gets a few punches in here and there.

You can hear the camera operator laughing as The Mountain — who has more than twice as much body weight — throws his arms up in a signature “Game of Thrones” move. Someone off-camera tries to help by yelling: “Start at the bottom and work your way up!” But this David-versus-Goliath match needs a lot more than simple strategy.

As The Mountain grabs McGregor’s leg, you get the feeling he could snap it off, but these two are undoubtedly friendly sparring partners. “Climb that mountain,” the off-camera voice advises. “The mountain slayer!”

Ultimately, Bjornsson gets down on his knees and playfully lets the opponent hop on his back. But frankly, McGregor should just consider himself lucky that he didn’t get his skull crushed.